• Nuclear Engineering and Technology
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• v.36 no.4
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• pp.357-363
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• 2004

A prototype long pulse ion source was developed, and the beam extraction experiments of the ion source were carried out at the Neutral Beam Test Stand (NBTS) of the Korea Superconducting Tokamak Advanced Research (KSTAR). The ion source consists of a magnetic bucket plasma generator, with multi-pole cusp fields, and a set of tetrode accelerators with circular apertures. Design requirements for the ion source were a 120kV/65A deuterium beam and a 300 s pulse length. Arc discharges of the plasma generator were controlled by using the emission-limited mode, in turn controlled by the applied heating voltage of the cathode filaments. Stable and efficient arc plasmas with a maximum arc power of 100 kW were produced using the constant power mode operation of an arc power supply. A maximum ion density of $8.3{\times}10^{11}\;cm^{-3}$ was obtained by using electrostatic probes, and an optimum arc efficiency of 0.46 A/kW was estimated. The accelerating and decelerating voltages were applied repeatedly, using the re-triggering mode operation of the high voltage switches during a beam pulse, when beam disruptions occurred. The decelerating voltage was always applied prior to the accelerating voltage, to suppress effectively the back-streaming electrons produced at the time of an initial beam formation, by the pre-programmed fast-switch control system. A maximum beam power of 0.9 MW (i.e. $70\;kV{\times}12.5\;A$) with hydrogen was measured for a pulse duration of 0.8 s. Optimum beam perveance, deduced from the ratio of the gradient grid current to the total beam current, was $0.7\;{\mu}perv$. Stable beams for a long pulse duration of $5{\sim}10\;s$ were tested at low accelerating voltages.

• Journal of Korean Society of Forest Science
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• v.105 no.3
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• pp.275-283
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• 2016

The objective of this study was to examine carbon dynamics with biomass, soil $CO_2$ efflux, litter and root decomposition after tree density control in young Pinus densiflora stands. The stands were established with 50% thinning, clear-cut, and control stands with three pseudo-replicated plots and a bare soil plot in 8-year-old Pinus densiflora nursery field. Monthly measurements were conducted from March 2012 to February 2014 and aboveground biomass and coarse-roots were estimated by derived allometric equations. Average diameter growth at root collar in control and thinned was 0.89 cm and 1.48 cm per year, respectively, and the diameter growth of control stand was significantly higher than that of thinned stands (p<0.05). Total biomass was estimated to 5.17, $4.85kg\;C\;m^{-2}$ per year in control and thinned, respectively. Annual soil $CO_2$ efflux in control, thinned, clear cut, and bare soil was 3.71, 3.90, 4.17, $4.56kg\;CO_2\;m^{-2}\;yr^{-1}$, respectively and removing trees significantly increased soil $CO_2$ efflux (p<0.05). Net Ecosystem Production (NEP) was 1.57, 1.36, -0.67, $-1.25kg\;C\;m^{-2}\;yr^{-1}$ in control, thinned, clear cut and bare soil in the young Pinus densiflora stands. NEP was significantly decreased by removing trees. Thinning increased diameter at root collar and carbon of individual tree and recovered 86% of carbon removed by thinning after one-year. In addition, soil $CO_2$ efflux increased and NEP increased by thinning. Results of this study, tree density control such as thinning increased the carbon storage and growth of the young Pinus densiflora stands.

• Korean journal of applied entomology
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• v.15 no.1 s.26
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• pp.7-16
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• 1976

In order to increase utility efficiency of red wood ants, Formica rufa truncicola var. yessonesis Forel as a resource of natural enemy of pine caterpillar, Dendrolimus spectabilis Butler, by finding out ecological and environmental factors in the habitat of red wood ants, the nest distribution and its density in habitat, plant distribution and density, stand-density of red pine, nest building and fixing plants, relative humidity of surface soil, physical and chemical natures of soil, and breeding rate were examined. The obtained results are summarized as follows: 1. The nest of red wood ants was densely distributed, in the lower-and middle top of mountain but no nest was found in the top. 2. The economical distribution of nest of habitat was estimated as $2.85/m^2$ and the lowest density as $1.93/m^2$ and these estimation lead us to confirm that pine caterpillar could be controlled. 3. The ecological characteristics of habitat seemed to be represented as higher stand-density of red pine of 10-20 years of age with large areas of eroded land under trees. The major grasses prevailing in this area were Andropogon brevifolius. Arundinella hirta, Miscanthus purpurasens, Eulia speciosa, Themeda japonica, Cymbopogon goeringii, and Eccoilpus cotulifer 4. Red wood ants seemed to build the nest by using red pine, Arundinella hirta, Miscanthus purpurascens, Themeda japonica or Cymbopogon goeringii as a fixing plant. 5. The limited point of humidity percent in habitat of red wood ants was estimated as $76\%$ during the acting period of May to September and as $72\%$ during pre-period of hibernation of October to November. 6. Soil analysis in habitating region showed higher concentration of organic matters and lower concentration of calcium and magnesium, and habitat was largely composed of silt and fine sand rather than coarse sand. 7. When the separated colony was transplanted to non-habitating red pine forest that seemed to have the similiar conditions as those of habitat, propagation and establishment of nest was possible.

• The Korean Journal of Physiology and Pharmacology
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• v.28 no.3
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• pp.275-284
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• 2024

Worldwide, cardiovascular disease is the main cause of death, which accordingly increased by hyperlipidemia. Hyperlipidemia therapy can include lifestyle changes and medications to control cholesterol levels. Statins are the medications of the first choice for dealing with lipid abnormalities. Rosuvastatin founds to control high lipid levels by hindering liver production of cholesterol and to achieve the targeted levels of low-density lipoprotein cholesterol, another lipid lowering agents named ezetimibe may be used as an added therapy. Both rosuvastatin and ezetimibe have low bioavailability which will stand as barrier to decrease cholesterol levels, because of such depictions, formulations of this combined therapy in nanotechnology will be of a great assistance. Our study demonstrated preparations of nanoparticles of this combined therapy, showing their physical characterizations, and examined their behavior in laboratory conditions and vivo habitation. The mean particle size was uniform, polydispersity index and zeta potential of formulations were found to be in the ranges of (0.181-0.72) and (-13.4 to -6.24), respectively. Acceptable limits of entrapment efficiency were affirmed with appearance of spherical and uniform nanoparticles. In vitro testing showed a sustained release of drug exceeded 90% over 24 h. In vivo study revealed an enhanced dissolution and bioavailability from loaded nanoparticles, which was evidenced by calculated pharmacokinetic parameters using triton for hyperlipidemia induction. Stability studies were performed and assured that the formulations are kept the same up to one month. Therefore, nano formulations is a suitable transporter for combined therapy of rosuvastatin and ezetimibe with improvement in their dissolution and bioavailability.

• Korean Journal of Environment and Ecology
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• v.34 no.3
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• pp.249-258
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• 2020

This study aims to provide reference material for effective forest management techniques at the catchment scale, based on the field investigation of large woody debris (LWD) in 11 streams within a third-order forest catchment in Gangwon Province, Korea. To achieve this aim, we analyzed the morphological features of LWD pieces, and the storage and distribution status of LWD by stream order throughout the entire investigation. As a result, a total of 1,207 individual pieces of LWD were categorized into three types as follows: (ⅰ) 1,142 pieces (95%) as only trunk and 65 pieces (5%) as a trunk with root wad, (ⅱ) 1,015 pieces (84%) as non-thinned and 192 pieces (16%) as the thinned, and (ⅲ) 1,050 pieces (87%) as conifer and 157 pieces (13%) as broadleaf. Additionally, in-stream LWD loads (㎥/ha) decreased with increasing stream order, yielding 105.4, 71.3, and 35.6 for first-, second-, and third-order streams, respectively. On the other hand, the ratio of LWD jams to the total LWD volume increased with increasing stream order, yielding 11%, 43%, and 49% for first-, second-, and third-order streams, respectively. Finally, a comparison of the in-stream LWD load with previous studies in several countries around the world indicated that in-stream LWD load was positively correlated with forest stand age even though the climate, topography, forest soil type, forest composition, stand growth rate, disturbance regime, and forest management practices were different. These results could contribute to understanding the significance of LWD as a by-product of forest ecosystems and an indicator of riparian forest disturbance. Based on this, we conclude that advanced forest management techniques, including treatment of thinning slash and stand density control of riparian forest by site location (hillslope and riparian zone, or stream order), should be established in the future, taking the forest ecosystem and the aquatic environment from headwater streams to low land rivers into consideration.

• Journal of Ecology and Environment
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• v.39 no.1
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• pp.1-10
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• 2016

Despite it has been mentioned that the successful restoration in landscape level was achieved in the Young-il soil erosion control project, quantitative evaluation of restored plant communities (Alnus firma as introduced species and Pinus thunbergii as native species) was hardly founded. Light availability, litter and woody debris cover, and forest structure and composition were determined for 500 m² band-quadrat in three forest types. Abiotic factors of Q. serrata stands, as reference forest, and A. firma stands were similar but not for P. thunbergii stands. There were no significant difference on mean stem density (stems ha^-1, H = 3.6, p = 0.162), and the mean basal area of each stand had marginal significance (m² ha^-1, H = 5.7, p = 0.058) among stands as total basal area was higher with the order of A. firma (21.4 m² ha^-1), P. thunbergii (19.8 m² ha^-1) and Q. serrata (16.2 m² ha^-1). Restoration of vegetation structure was more effective in fast-growing and N-fixing A. firma, as introduced species plantation. However, result of MRPP, NMS ordination and ISPAN for herbaceous layer, not for tree and shrub species composition, indicated that restoration of ground vegetation was likely influenced highly from local environment. Propagule availability from landscape context such as connectedness to natural vegetation and management practices in restored isolated stands are available explanations for restoration effects and gaps between restored plantations and secondary oak forest.

• Journal of Korean Society of Forest Science
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• v.107 no.1
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• pp.1-15
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• 2018

In order to determine the effects of thinning on mushroom fruiting, microclimate and air temperature in Quercus mongolica forests, this study investigated changes in crown density, soil temperature, air temperature and throughfall in the natural Q. mongolica forest which was thinned by approximately 45% four years ago. The results showed that crown density was smaller than control by 6% from April to October, The soil temperature and air temperature in the thinned stands were significantly higher than those of the control by $1{\sim}2^{\circ}C$ until August and differences in air and soil temperature. The average daily temperature difference was higher than control by $0.2{\sim}0.7^{\circ}C$ until October. Throughfall from July to September in the thinned was approximately 135 mm higher than in the control. The maximum difference in throughfall per unit time was 3.5 mm/h. Soil moisture in the thinned site increased by approximately 5% compared with the control and reduced to the normal moisture after 4 days in both sites. 55 mushroom species were found in the thinned area between July and September. The thinned site contained 10 mycorrhizal mushrooms more than the control and 1 saprophytic mushroom species more than the control. Shannon-Wiener Index was 3.2, approximately 0.5 higher than the control. Tylopilus neofelleus, etc., occurred in the thinned site more quickly, but Aaricus subrutilescens, Clitocybe sp, occurred later. In the thinned site, the dominance of Tylopilus neofellelus and Armillaria sp. increased approximately 6% and 30% and yield about 1.5 times and 20 times, respectively. In conclusion, thinning in the Q. mongolica forest increased the soil and air temperature, soil moisture, throughfall and the diversity of mushroom species, and advanced the period of occurrence, and increased dominance and yield of some mycorrhizal mushrooms and Amillaria sp.

• Journal of Korean Society of Forest Science
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• v.87 no.3
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• pp.328-333
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• 1998

To obtain basic information for establishing a pest control strategy for insect pest management system, changes in the population densities of the black-tipped sawfly(Acantholyda posticalis posticalis Matsumura) and damage patterns in tree growth were investigated in national forests in Hoigok-ri, Kapyung-gun, Kyunggi-do, where the pest control measures were taken. The results obtained were as follows ; 1. The larval density in the soil of the forests where the insecticides were applied have been kept below economic threshold for about 7 years. The density was the highest in the middle of slopes and similar to the level of the early stage of the insect outbreak. 2. After the pest control by insecticides, reduction in tree height and diameter growth lasted for 2-3 years in trees defoliated by over 70%. 3. The diameter growth of the trees damaged by black-tipped sawfly recovered faster in upper stem than in the lower. 4. volume growth of the trees defoliated over 70% by the insect decreased for three to four years. The volume loss of trees defoliated by 70% and 90% was 19.6% and 54.0%, respectively. 5. Maintaining the rate of defoliation below 50%, which is the economic threshold, by chemical control measures had an effect of reducing the tree volume loss by $40m^2/ha$ as compared with a stand defoliated by 90%.

• Journal of Bio-Environment Control
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• v.21 no.2
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• pp.114-119
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• 2012

We have conducted 4 experiments to develop the most environmental and effective use of the two-fluid fog system to prevent and exterminate whiteflies in tomato cultivation. In particular, these experiments used Vitamini tomatoes grown in stand-alone greenhouses at Buyeo Tomato Experiment Station as subjects. Each experiment utilized the fog system in a different way. The first experiment provided the control group, which was subject to the two-fluid fog system without additional humidity control. In the second experiment, the two-fluid fog system controlled the humidity level to be above 70%. The third and the fourth experiment utilized natural substances, which were 1.5 mg/L of Neem Oil and 2 mg/L of Oleic acid respectively, without additional humidity control. From the first experiment, we could observe that a simple use of the two-fluid fog system decreased the density of whiteflies in the greenhouses. This impact of the fog system on whiteflies was greater in the second experiment. By comparing the first and the second experiment, we concluded that whiteflies are more effectively prevented by maintaining a higher humidity level via the fog system's smaller water droplets that float in the air for longer time than the standard fog system in rather dry condition. In the third and the fourth experiments, the extermination level was 78% and 76.4% respectively, comparing only 53% in the first experiment without the humidity control. Therefore, using the natural substances in addition to the humidity control increases the extermination effectiveness. Considering the similar results from the 3rd and the 4th experiments, Oleic acid has a greater appeal for its lower price. Using the two-fluid fog system to both control the humidity on a daily basis and spray the substances for occasional extermination would reduce labor cost and increase production in an environmental way.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.6
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• pp.409-414
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• 2009

In 1970's Black locust(Robinia pseudoacacia) had been widely planted Korea as an important forest greening species for erosion control afforestation. Since 2000, however, the tree's leaf-yellowing symptom has often been observed at a limited region and then spreaded out over the country in 2006. This study was conducted to study soil physiochemical properties of black locust stands with and without the leaf-yellowing symptom in Osan, Gyeonggi province. Most of soils in sampling sites were mostly slightly eroded, dry, and moderately dry. Available soil depth(16cm) and total soil depth(26cm) in leaf-yellowing (LY) site were significantly lower than in non leaf-yellowing (Non-LY) site's soil depths which were 30cm and 56cm, respectively. And solid phase proportion and bulk density in soils were lower in LY site than in non-LY site soils, while soil liquid phase proportion was also low. It could reflect that LY site soils might have a lower air and moisture movement in the rhizosphere of black locust stand compared with non-LY site soils. Soil acidity in both sites was very strong acid, soil pH (4.42) of LY site was slightly lower than non-LY site's (pH 4.54). Content of available phosphorous, exchangeable $Ca^{2+}$ and $Mg^{2+}$ and percent base saturation were less than LY site. These results indicated that soil physiochemical condition in LY site, more deteriorated than non-LY site, should adversely affect the retention and supply capacity of soil nutrients and moisture. Therefore the black locust may be more sensitive to other environmental stresses.