• Journal of Korean Society of Forest Science
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• v.83 no.1
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• pp.50-62
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• 1994

This study is performed to consider the fitness of natural regenerating method and tending methods used now by surveying the stand structure and regenerating states of the 9 natural regenerated Pinus densiflora stands in Kangwon province. As a special consideration, it deals with the tending methods on the seedlings of Pinus densiflora and broad-leaved tree(Quercus mongolica) under competition. By the consideration on the number of trees, growing capacity and stand structures of Pinus densiflora stands, it reveals that Pinus densiflora is in the inferior in numbers at the competition to the broad-leaved species, and it could not occupy the stands as the dominant species if the stands were not tended. It is estimated that natural regeneration of Pinus densiflora stands by the clearcutting or seed tree system could not achieved due to the abundance of ground vegetation. Short-term shelter-wood system or strip stand method may be proposed as a successful method of natural regeneration. As the visible tending method for seedlings, the method which apply the mixed forest in group of Pinus densflora and Quercus mongolica different by the growing capacity and distribution characteristics is better thaw the one which tend the Pinus densiflora only.

• Journal of the Korean Geosynthetics Society
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• v.16 no.3
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• pp.21-30
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• 2017

Cement grouting method is generally applied for the purpose of reinforcement of deteriorated reservior. Problems have been raised due to the limit of the injection material. In order to solve these problems, various grout materials have been developed. However, there are many cases in which the grounds are disturbed in actual field. In this study, the physical properties of hybrid grout with high fineness and high viscosity characteristics were analyzed to enable penetration into the ground. Optimum inflation agent was selected and mixed with the grout. The pressure and compaction effect on expansion was examined and its effectiveness was verified. From the result of confirming expansion ratio, uniaxial compressive strength, expansion pressure and compaction effect, the HI-E (2%) sample was analyzed to be excellent in improvement effect by the inflation agent. Hence, hybrid grout can be effectively applied for the impermeable and reinforcement method of deterioration reservoir and tide embankment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.170-178
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• 2015

In this study, it was developed eco-friendly alkali-activated slag fiber reinforced concrete using ground granulated blast furnace slag, alkali activator (water glass, sodium hydroxides), and steel fiber. Eight reinforced concrete beam using alkali-activated slag concrete were constructed and tested under monotonic loading. The major variables were mixture ratio of alkali activator, mixed/without of steel fiber. Experimental programs were carried out to improve and evaluate the flexural performance of such test specimens, such as the load-displacement, the failure mode, the maximum load carrying capacity, and ductility capacity. All the specimens were modeled in scale-down size. The reinforced concrete beams using the eco-friendly alkali-activated slag fiber reinforced concrete was failed by the flexure or flexure-shear in general. In addition, the maximum strength increased with the adding the mol of sodium hydroxide, and the specimen reinforced the steel fiber showed the value of maximum strength which is increased by 15.8% through 25.9%. It is thought that eco-friendly alkali-activated slag fiber reinforced concrete can be used with construction material and product to replace normal concrete. If there is applied to structures such as precast concrete member and production of 2nd concrete product, it could be improved the productivity and reduction of construction duration etc.

• The Journal of Korean Academy of Prosthodontics
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• v.17 no.1
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• pp.23-34
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• 1979

In this study, the adhesive strength of three commercial polycarboxylate cements to ten types of dental casting alloys, such as gold, palladium, silver, indium, copper, nickel, chromium, and human enamel and dentine were measured and compared with that of a conventional zinc phosphate cement. The $8.0mm{\times}3.0mm$ cylindrical alloy specimens were made by casting. The enamel specimens were prepared from the labial surface of human upper incisor, and the dentine specimens were prepared from the occulusal surface of the human molar respectively. Sound extracted human teeth, which had been kept in a fresh condition since, extraction, were mounted in a wax box with a cold-curing acrylic resin to expose the flattened area. The mounted teeth were then placed in a Specimen Cutter (Technicut) and were cut down under a water spray, and then the flat area on the all specimens were ground by hand with 400 and 600 grit wet silicone carbide paper. Two such specimens were then cemented together face-to-face with freshly mixed cement, and moderate finger pressure was applied to squeeze the cement to a thin and uniform film. All cemented specimens were then kept in a thermostatic humidor cabinet regulated at $23{\pm}2^{\circ}C.$ and more than 95 per cent relative humidity and tested after 24 hours and 1 week. Link chain was attached to each alloy specimen to reduce the rigidity of the jig assembly, and then all the specimens were mounted in the grips of the Instron Universal Testing Machine, and a tensile load was delivered to the adhering surface at a cross head speed of 0.20 mm/min. The loads to which the specimens were subjected were recorded on a chart moving at 0.50 mm/min. The adhesive strength was determined by measuring the load when the specimen separated from the cement block and by dividing the load by the area. The test was performed in a room at $23{\pm}2^{\circ}C.$ and $50{\pm}10$ per cent relative humidity. A minimum of five specimens were tested each material and those which deviated more than 15 per cent from the mean were discarded and new specimens prepared. From the experiments, the following results were obtained. 1) It was found that the adhesive strength of the polycarboxylate cement to all alloys tested was considerably greater than that of the zinc phosphate cement. 2) The adhesive strength of the polycarboxylate cements was superior to the non precious alloys, such as the copper, indium, nickel and chromium alloys, but it was inferior to the precious gold, silver and palladium alloys. 3) Surface treatment of the alloy was found to be an important factor in achieving adhesion. It appears that a polycarboxylate cement will adhere better to a smooth surface than to a rough one. This contrasts with zinc phosphate cements, where a rough helps mechanical interlocking. 4) The adhesion of the polycarboxylate cement with enamel was found superior to its adhesion with dentine.

• Journal of the Korean GEO-environmental Society
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• v.18 no.10
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• pp.23-34
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• 2017

As the electrical property of fully saturated soils is dependent on the pore water, it has been commonly used for the detection of the contamination into the ground. The objective of this study is to investigate the electrical characteristics according to the salinity and the lead concentration in fully saturated soils. Fresh water and saline water with the salinity of 1%, 2% and 3%, which are mixed with 6 different lead solutions with the range of 0~10 mg/L, are prepared in the cylindrical cell incorporated with sensors for measuring electrical resistance and time domain reflectometry signal. Then, the dried sands are water-pluviated into the cell. The electrical resistance and the time domain reflectometry signal are used to estimate the electrical conductivity. Test results show that electrical conductivity determined from electrical resistance at the frequency of 1 kHz continuously increases with an increase in the lead concentration, thus it may be used for the estimation of the contaminant level. In addition, the electrical conductivity estimated by the time domain reflectometry changes even at very low concentration of lead, the variation rate decreases as the lead concentration increases. Thus, the time domain reflectometry can be used for the investigation of the heavy metal leakage. This study demonstrates that complementary characteristics of electrical resistance and time domain reflectometry may be used for the detection of the leakage and contamination of heavy metal in coastal and marine environments.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.9
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• pp.1462-1467
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• 2007

This study investigated the effect of chemical treatments on tannins (condensed and hydrolysable) and on the trypsin inhibitor (TI) activity in salseed meal. Triplicate samples of ground salseed meal (1 kg) were mixed with 820 ml of either distilled water (pH 5.3), 0.67 M acetic acid (pH 2.4), 0.67 M sodium bicarbonate (pH 8.2) or 2% polyvinyl-pyrrolidone (PVP) solution. The material was placed in airtight plastic containers and incubated at $37^{\circ}C$ for 0, 3, 6, 12, 24, 48 and 72 h. Samples of untreated salseed meal which had not been subjected to soaking or incubation were run through the analysis to serve as control. Addition of water, acetic acid, sodium bicarbonate and PVP solutions to salseed meal and subsequent anaerobic incubation at $37^{\circ}C$ significantly reduced chemically detectable tannins. At each incubation time, alkali solution was more effective than its counterparts. The effect of acidic solution on hydrolysable tannin was least among the treatments. All the treatments reduced TI activity of salseed meal. The reduction in TI activity by these treatments was similar and ranged between 80-84%. Treatment time effected a decrease in the contents of antinutritional substances. However, the effect of the treatment with the reagents, even for zero incubation time, was quite pronounced. It may be concluded from the present results that the treatment of salseed meal with sodium bicarbonate (0.67 M) is more effective in reducing hydrolysable and condensed tannin contents than PVP, water and acid solutions. Treatment with sodium bicarbonate solution is more economical and easier to handle than acid and PVP treatments. Incubation of the treated material for 12 h is reasonably effective, economical and safe from any mould growth.

• Journal of Life Science
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• v.9 no.2
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• pp.194-200
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• 1999

Grinding aid is a necessary unit operation when the raw materials are handled in solid form, and the purpose is to improve the bioavailability by reducing the particle size. For the particle design of pefloxacin, the dry planetary ball-mill was used. With the drying process, 330 g of zirconia ball with its size of 2 mm in diameter and 10 g of pefloxacin were transferred to the pot and mixed well. The mixture was ground at 112 rpm (60 Hz) for 15, 30, and 60 min, respectively. The most satisfactory grinding products were generated at 15 min of grinding time for their particle size. The volume mean diameter $\X_50$ of the grinding products was 2.97 $\mu$m. X-ray diffraction (XRD), differential scanning calorimeter (DSC), and infrared spectroscopy (IR) patterns were relatively unchanged before pulverizing pefloxacin and in the progress of grinding. Thus, these results suggest that this pulverizing method can be used for grinding products without evident effect on stability of the drug pefloxacin. Dissolution test was carried out to set up the optimal detective condition against residual antibacteria of fish by HPLC. The grinding pefloxacin for 15 min is most effective in dissolution test.

• Journal of Animal Science and Technology
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• v.46 no.3
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• pp.443-450
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• 2004

To examine the potentiality of grassland dominated with turf-type grasses, which are mainly used for the establishment of green spaces, forage production and its utilization as forage resources, dry matter yield and forage quality of three different turf-type mixtures were estimated throughout three consecutive experimental years. According to the experiment, the mean of dry matter(DM) yield, chemical composition, DM digestibility, crude protein dry matter(CPDM) and digestible dry matter(DDM) yield was not significantly different among species(p > 0.05) over three experimental years. Botanical composition of three dominant species(tall fescue, Kentucky bluegrass and perennial ryegrass) was 42, 35 and 28%, respectively, in three mixtures at the last cutting(6th) in 2001. The botanical composition of three dominated species such as tall fescue, Kentucky bluegrass and perennial ryegrass was maintained 84% of the total plants in all types of mixtures. Therefore, It is observed that the mixture types did not closely affect the botanical composition. But botanical composition of the other species such as redtop(8%) and creeping bentgrass(6${\sim}$7%) was low. Especially, that of red fescue was the least(1${\sim}$2%) of all mixed species. As mentioned above, any difference was not observed in DM yields, forage quality and botanical composition among mixture types. Therefore, any types of mixtures can be used as public green spaces like school ground areas or river-sides, and as forage resources additionally.

• The Korean Journal of Soil Zoology
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• v.5 no.2
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• pp.47-62
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• 2000

This study investigated the effect of soil animals at forest fire area, and it carried out the mountain located at Jundae Ri, Houeng-chen Myen, Ha-dong Gun, Kyoung-Nam Province, southern part of Korea, where burned out about 50 hectars on April 11, 1997. Vegetation of the examined area absolutely dominated with the pines of 7-14 cm in diameter and 20 to 30 years old and the rest were covered with mixed forest with a shrub such as the oak (Quereus mongolia Fisch, Quereus variabilis BI, Quereus dentana Thunb), snowbell(Styrax japonica, S, et, z), lacquer tree (Rhus trichocarpa Mig), azalea (Rhododendron mucronulatum Turcz), etc. And there were simple area organized as a herbaceous plant, and the burnt area was poor experimental sites, where litter layer and herbaceous plant disappeard due to fire, and the unburnt area was rich in surface plant, dead leaves, twigs, etc. But the ground cover vegetations were poor in the unburnt area. The distribution of each animal groups, the seasonal fluctuation in population density, the biomass of meso$.$macroarthropods and the relationship between soil animal and some environmental factors were investigated and analyzed at each experimental area. The result are summarized as follow: 1. Identificated 257,087 individuals of soil microarthropods were classified into 7 classes and 24 orders of Arachinida, Insecta, Chilopoda, Symphyla, Diplopoda, Isopoda and Oligochaeta., and identified 8,006 individuals of the total meso$.$macroarthropods were classified into 7 classes and 20 orders of Arachinida, Insecta, Chilopoda, Symphyla, Diplopoda, Isopoda and Oligochaeta. 2. Among the total soil microarthropods, Arachinida formed 70.9%, followed by Insecta for 28.4% and among the total meso$.$macroarthropod , Insecta formed 57.6%, followed by Chilopoda for 23.8%.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.20 no.6
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• pp.117-131
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• 2017

This study was conducted to draw vegetation landscape elements in the ancient literature, investigate plant community structure, understand vegetation structure, and suggest reasonal conservation management methods. As a result of analyzing ancient literature, geomorphological landscapes in Guryong valley were canyon landscape and valley surrounded in Mt. Chiak. Plant landscape factors were as followed. Rhododendron spp. spread around valley. Also, Pinus densiflora communities were distributed in Guryong valley around. Especially, the entrance zones of Guryong valley were described as covered with Pinus densiflora and Whangchangkumpyo(黃腸禁標). Therefore, it was estimated that entry of Guryong valley was covered with Pinus densiflora community landscape. As for current vegetation result, the main vegetation was divided into mixed deciduous broad-leaved trees community and Pinus densiflora community. As a result of analysis by TWINSPAN for community classification, five communities(Deciduous broadleaved trees, Pinus densiflora, Pinus densiflora-Abies holophylla, Abies holophylla, and Pinus koraiensis community) were classified. To maintain historic plant landscape and conserve crucial resources, Pinus densiflora community was classified as concentrated conservation management area($105,472m^2$). To maintain Pinus densiflora landscape which has high historical and cultural value of Guryong valley, it was considered that active density control of lower layer vegetation would be necessary. Accordingly, to conserve P. densiflora landscape, Whangchangkumpyo(?腸禁標), that area was separated into Pinus densiflora lower layer forest management area($84,029m^2$) and Pinus densiflora seedling conservation management area($21,443m^2$). In understory of Pinus densiflora lower layer flora, the target tree species for elimination and management were Quercus serrata and Quercus mongolica. They were $4{\sim}6trees/100m^2$ and their average diameter was 7.1cm. To preserve Pinus densiflora seedlings, areas with Sasa borealis, the ground vegetation of Pinus densiflora community, rate of 80% or more should be selected as priority management areas and concentrated elimination and management of Sasa borealis should be implemented. Likewise, traditional Pinus densiflora forest is a historically cultural heritage to preserve with sustainable interest and survey. Efficient management method through systematic monitoring system should be made.