• Korean Journal of Medicinal Crop Science
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• v.22 no.6
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• pp.463-468
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• 2014

This study was carried out in order to survey the soil physico-chemical, morphology and content of saponins of 5 year-old Platycodon grandiflorum radix from different areas in Gyeongnam. Soil physical properties was showed 1.01-1.29 of bulk density of soil and soil hardness was increased with increasing soil depth, especially below the 30 cm, however it was maintained or small increased below the 40 cm. T-N and OM contents of top soil were highest at Geochang as 0.27% and 56.9 g/kg, respectively, compared to other areas. The root length was longer at Kimhea and Geochang as 33.8 and 33.7 cm, respectively, and fresh weight was heavy at Geochang as 208.5 g. The contents of saponin of P. grandiflorum radix was higher in fine root compare to main root. By region, content of saponins of P. grandiflorum radix were higher at Hapcheon than other area. Mg content was highly negatively correlated at p < 0.01 with platycodin D3, deapioplatycodin D, platycodin D, and deapioplatycodin D ($-0.499^{**}$, $-0.433^{**}$, $-0.421^{**}$, $-0.511^{**}$ respectively). These results suggest that no-fertilized Mg effected on the improvement of saponin contents in P. grandiflorum.

• Tunnel and Underground Space
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• v.25 no.3
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• pp.231-243
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• 2015

In this study, both in-situ stress measurements and a lot of laboratory rock tests were conducted at a metal mine in Jeongseon, Korea. The stress ratio obtained from in-situ stress measurements showed a tendency to decrease according to depth below surface and its average value was 1.10. The mechanical properties such as unit weight, absorption ratio, porosity, elastic wave velocity, uniaxial compressive strength, Young's modulus, Poisson's ratio, tensile strength, shore hardness, friction angle and cohesion were investigated for the four different rocks mainly distributed at a studied mine, which were dolomite, felsite, granite and magnetite. The mechanical properties of the four different rocks were compared by means of statistical analyses, whereupon the felsite and the granite turned out to have more strength characteristics than the magnetite. The correlation of mechanical properties was also investigated, whereupon a few results against the general correlation were found out. The failure criteria of the four different rocks were finally discussed by means of both Mohr-Coulomb criterion and Hoek-Brown criterion.

• Journal of Environmental Impact Assessment
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• v.7 no.2
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• pp.37-51
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• 1998

This study was carried out to lead the scientific management of the urban forest by estimating the forest environment. Forest environmental information was constructed using IDRISI system based on survey data, soil, plant, and digital elevation data. Forest environmental information was consisted of soil depth, soil organic content, soil hardness and parent rock as a soil environmental factor, and forest community, tree age, crown density as a plant environmental factor. Plant activity and topographic environment also were analyzed by using remote sensing data and digital elevation data. Environmental function of urban forest was estimated based on results of soil conservation and forest productivity. 70% of urban forest is located in elevation of lower than 200m and 55% of forest area have the slope of lower than 15 degree. Analyzed soil conservation status and forest productivity were almost the same as the soil chemical properties of collected soil sample and the vegetation index estimated using remote sensing data, respectively. Thus, the constructed forest environmental information could be useful to give some ideas for management of urban forest ecosystem and establishment of environmental conservation planning, including forests, in Taejon. The best forest environmental function was appeared at the natural ecology preservation zone. Current natural parks and urban parks were appeared to establish the environmental conservation plan for further development. The worst forest environmental function was appeared at the forest near to the industrial area and an overall and systematic plan was required for the soil management and high forest productivity because these forest was developing a severe soil acidification and having a low forest productivity.

• Korean Journal of Materials Research
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• v.23 no.5
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• pp.293-298
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• 2013

In this study, an HP-mod. type(KHR-45A), which is used as a heater tube material in the pyrolysis process, was evaluated for its carburizing properties. It was confirmed from the microstructural observation of the tubes that the volume fraction of carbide increased and that the coarsening of Cr-carbide generated as a degree of carburization increased. The depth of the hardened layer, which is similar to the thickness of the carburized region of each specimen, due to carburization is confirmed by measurement of the micro-Vickers hardness of the cross section tube, which thickness is similar to that of the carburized region of each specimen. Two types of chromium carbides were identified from the EBSD (electron back-scattered diffraction) image and the EDS (energy-dispersive spectroscopy) analysis: Cr-rich $M_{23}C_6$ in the outer region and Cr-rich $M_7C_3$ in the inner region of tubes. The EDS analysis revealed a correlation between the ferromagnetic behavior of the tubes and the chromium depletion in the matrix. The chromium depletion in the austenite matrix is the main cause of the magnetization of the carburized tube. The method used currently for the measurement of the carburization of the tubes is confirmed; carburizing evaluation is useful for magnetic flux density measurement. The volume fraction of the carbide increased as the measuring point moved into the carburized side; this was determined from the calculation of the volume fraction in the cross-section image of the tubes. These results are similar to the trends of carburization measurement when those trends were evaluated by measurement of the magnetic flux density.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.633-642
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• 2008

It's important to measure quantitative properties about thermal-nano behavior of polymer for producing high quality components using Nanoimprint lithography process. Nanoscale indents can be used to make the cells for molecular electronics and drug delivery, slots for integration into nanodevices, and defects for tailoring the structure and properties. In this study, formability of polymethylmetacrylate(PMMA) and polycarbonate(PC) were characterized Polymer has extreme variation in thermo mechanical variation during forming high temperature. Because of heating the polymer, it becomes softer than at room temperature. In this case it is particularly important to study high temperature-induced mechanical properties of polymer. Nanoindenter XP(MTS) was used to measure thermo mechanical properties of PMMA and PC. Polymer was heated by using the heating stage on NanoXP. At CSM(Continuous Stiffness Method) mode test, heating temperature was $110^{\circ}C,120^{\circ}C,130^{\circ}C,140^{\circ}C$ and $150^{\circ}C$ for PMMA, $140^{\circ}C,150^{\circ}C,160^{\circ}C,170^{\circ}C$ and $180^{\circ}C$ for PC, respectively. Maximum indentation depth was 2000nm. At basic mode test, heating temperature was $90^{\circ}C$ and $110^{\circ}C$ for PMMA, $140^{\circ}C,160^{\circ}C$ for PC. Maximum load was 10mN, 20mN and 40mN. Also indented pattern was observed by using SEM and AFM. Mechanical properties of PMMA and PC decreased when temperature increased. Decrease of mechanical properties from PMMA went down rapidly than that of PC.

• Journal of Korean society of Dental Hygiene
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• v.17 no.5
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• pp.817-826
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• 2017

Objectives: The aim of this study was to investigate the effects of bamboo salts on remineralization effects on subsurface of artificial carious enamel. Methods: Incipient carious enamel was formed in permanent bovine incisors and then specimens were divided into three groups randomly: 3% bamboo salt (BS), 2% (NaF) and the solution of mixed 3% BS and 2% NaF. For remineralization, specimens of each of the three groups were treated for 24 hrs at $37^{\circ}C$ incubator. After treatment, specimens were analyzed using SEM and VHN. Statistical analysis used was one-way ANOVA. Results: In SEM observation, the BS group showed narrower distances between enamel rods than the cases of incipient subsurface caries enamel. The NaF and BS+NaF groups showed that the enamel rods near the surface were destructed, and innumerable round small particles were deposited near the surface of enamel. The BS+NaF group showed more minerals attachment between enamel rods than the cases of other groups. The differences in subsurface microhardness (${\Delta}VHN$) increased all of three groups in total by $80{\mu}m$. The ${\Delta}VHN$ of the BS+NaF group increased significantly more than NaF and BS groups in depth of $50{\mu}m$, $80{\mu}m$. Conclusions: The 3% bamboo salt with 2% NaF solution was found to increase subsurface hardness of incipient caries enamel. Thus, bamboo salt will be used to contribute to prevention on dental caries.

• Journal of Biosystems Engineering
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• v.27 no.1
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• pp.25-32
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• 2002

This study was conducted to develop a dry paddy seeder of strip tillage. The prototype is 8 rows drill seeder, which is composed of a strip tillage, sowing and fertilizing device, and pressing wheels to do the strip tillage, sowing, fertilizing, and draining ditch, simultaneously. The performances of prototype was evaluated through the investigation of fuel consumption, tillage torque, ratio of soil breaking, and economical efficiency and the results were compared with these of a dry paddy seeder that needs whole tillage. According to the USDA textural classification, the experiment field was composed of sandy loam which consisted of 56.8 of sand, 30.2 of silt and 13.0 % of clay, respectively. Its hardness ranged from 952 to 1,673 kPa depending on the soil depth, and its soil moisture content was 24.9%(d. b.) Fuel consumption of the prototype was 5,015g/hr at 2,000 rpm of engine, which was consequently 64% smaller than that of the conventional dry paddy seeder. For the tillage torque, it ranged from 132 to 206N$.$m depending on the tillage pitch, which was 10∼30% smaller than that of the conventional dry paddy seeder. The ratio of soil braking of the prototype was 87∼98%, whereas that of the conventional dry paddy seeder was 80∼97%. The working performance of the prototype was surveyed to be 3.8hours/ha, which was about 5 times higher than that of the conventional dry paddy seeder. The cost reduction of 26.3% was obtained by using the prototype.

• Tribology and Lubricants
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• v.30 no.6
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• pp.343-349
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• 2014

Currently, in order to resist the scratching of the fuel rod surface while fabricating the fuel assembly of the light-water nuclear reactor, we use a solution of nitrocellulose, an explosive material, as a dry lubricant along with its solvent. However, the demand for developing safe and harmless aqueous alternative materials for environment-conservation and field-worker safety has increased. In this study, we demonstrate the preparation of a novel aqueous resin composite using a formulation of aqueous polymeric resin, alcoholic solvent, and water. Subsequently, we characterize this composite on the basis of hardness, adhesive property, and water solubility using plates similar to the fuel rod material. The insertion test of a fuel rod coated with the YS-3 composite shows load values of $18.8-20.5kg/cm^2$, which is comparable with $18.8-20.5kg/cm^2$ of the nitrocellulose coating agent. In addition, the depth and width of longitudinal scratches caused by the YS-3 composite test are 50% higher than those of the standard. We can develop a harmless and safe aqueous dry lubricant to replace the existing NC products through field testing of 264 pieces of fuel rods, after producing 350 kg of the YS-3 prototype. The scratch test for the rod surface showed that weight of chip of YS-3 prototype was smaller than that of NC before and after solvent treatment, indicating the properties of YS-3 prototype was comparable to the counterpart.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.40-48
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• 1995

$TiB_2$-TiN double-layer coating have been prepared by ion beam enhanced deposition. AES, XRD, TEM and HRTEM were employed to characterize the $TiB_2$ layer. The microhardness of the coatings was evaluated by an ultra low-load microhardness indenter system, and the tribological behavior was examined by a ball-on-disc tribology wear tester. It was found that in a single titanium diboride layer, the composition is uniform along the depth of the film, and it is mainly composed of nanocrystalline $TiB_2$ with hexagonal structure, which resulted from the ion bombardment during the film growth. The hardness of the $TiB_2$ films increases with increasing ion energy, and approaches a maximum value of the $TiB_2$ films increases with increasing ion energy, and approaches a maximum value of 39 Gpa at ion energy of 85 keV. The tribological property of the TiB2 films is also improved by higher energy of 85keV. The tribological property of the $TiB_2$ films is also improved by higher energy ion beam bombardment. There is no major disparity in the mechanical properties of double-layer $TiB_2$/TiN coatings and TiN/$TiB_2$ coatings. Both show an improved wear resistance compared with single-layer $TiB_2$ films. The adhesion of double-layer coatings is also superior to that of single-layer films.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.3
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• pp.5-12
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• 1990

This study has been conducted to establish the carburizing characteristics of low carbon alloy steels with varying amount of Ni element gas-carburized for 2 hours at $930^{\circ}C$ in an atmosphere of 94% $N_2$-6% $C_3H_8$ gas mixture with some changes in gas pressure passing through the diffusion plate in the fluidized-bed furnace. The results obtained from the experiment are as follows : (1) Optical micrograph has shown that the carburized layer consists of retained austenite and plate martensite and that retained austenite increases as the pressure of gas mixture passing through the diffusion plate as well as Ni content increase. (2) Chemical analysis has shown that carbon potential increases and carburizability is also improved due to a less degree of fluidization as the pressures of gas mixtures passing through the diffusion plate increase, resulting in, however, a severe formation of soot, and the gas pressure is necessarily regulated. (3) It has been revealed that carbon concentration hardness values at a given distance measured from the surface within the carburized case. Increase with increasing the pressure of gas mixtures passing through the diffusion plate and decrease with increasing Ni content. (4) The effective case depth has been shown to almost linearly increase as the pressure of gas mixtures passing through the diffusion plate is increased and to decrease with increasing Ni content.