• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.4
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• pp.271-279
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• 2016

The objective of this study was to determine the effect of the moisture content and pellet mill type on the physical and chemical characteristics of Italian ryegrass (IRG) pellet. Moisture content of raw material significantly (p<0.05) affected IRG pellet formation. Moisture content at 25% was the best condition for IRG pellet formation in terms of shape, power load and temperature changes. The hardness of pellet was decreased when moisture content was increase. However, the hardness of pellet was not affected by pellet mill type. Moisture content at 30% dramatically (p<0.05) decreased the durability compared to moisture content at 25%. Dry matter content of IRG pellet was increased (p<0.05) after pelleting. Total count of microorganism was decreased in pellet due to pressure heat and moisture losses during the pelleting process. These results indicated that the proper moisture content of Italian ryegrass pelleting would be at 25%. In addition, Roll & flat die type would be more suitable than Ring die and Die & flat die type in IRG pelleting. Pelleting works would be beneficial for improving forage quality and long storage.

• Korean Journal of Agricultural Science
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• v.42 no.3
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• pp.191-199
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• 2015

We conducted this research to observe the changes of surface morphology and composition of clay minerals influenced by various concentrations of fluoric acid. Hydrofluoric acid (HA), a solution of hydrogen fluoride (HF) in water, is a colourless solution that is highly corrosive, capable of dissolving many materials, especially oxides. To do this, we treated several concentrations of HA on the ground soil samples collected from the agricultural experimental station located at Chungnam National University to observe the influence of fluoric acid on the changes of surface structures and elemental composition of clay particles. Generally, microscopic examination showed that the HA can not only attack an edge of clay particles but also start at any point where structural defects and weaknesses predisposed sites to acid. The orderly flake arrangement of clay minerals may reflect certain crystal symmetry elements. The ESEM-EDS results of element composition of clay particles influenced by HA indicated the changes of structures of clay minerals. It is also clear from the formation of etch figures and element composition of clay particles that the product layer at least partially dissolved or disintegrated in the presence of acid. Conclusively, the clay structures can be strongly influenced by concentrations of HA, resulting in changes of physical and chemical properties that can determine the behavior of solute transport as well as mobility of ions in soils.

• Journal of Korea Spatial Information System Society
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• v.10 no.2
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• pp.81-93
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• 2008

Current re-arrangement of river and waterway has been made uniformly ignoring characteristics of individual rivers thereby aggravating artificial river restructuring. Subsequently this severely affects the rivers' physical, chemical, and biological phenomenon. On the contrary, quantitative techniques to evaluate the aftermath of artificial river disturbance such as uprising of river bed, intrusion of foreign fisheries, and changes of ecological habitats are not available. To establish such quantitative techniques, analysis of river changes to evaluate the major causes of the river disturbance and its impacts is essential. Therefore, this study mainly focused on proposing a method which can be applied for the development of techniques to investigate river disturbance according to the major factors for the domestic rivers using airphotos and GIS techniques. For the analysis, the study area on the downstream of the river was selected and airphotos of the area were converted into GIS format to generate 'shape' files to secure waterways, river banks, and auxiliary data required for analyzing river disturbance. Trend analysis of the waterway sinuosity and changes of the flow path leaded to detailed verification of the river disturbance for specific location or time period, and this enabled to relatively accurate numbers representing sinuosity of the waterway and relevant changes. As the major results from the analysis, the relocation of waterways and the level of river sinuosity were quantified and used to verify the impacts on the stability of the waterways especially in the downstream of the dam. The results from this study enabled effective establishing proper measures against waterways' unstability, and emphasized subsequent researches for identifying better alternatives against river disturbances.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.1
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• pp.25-35
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• 2010

The periodic application effects of two different herbicides on soil physical properties were observed in a slightly hilly orchard of pear tree located on the southestern flank of the Palbong Mountain in Gongju Chungnam : (1) bare surface vegetation; (2) glyphosate-treated plot; (3) paraquat-treated plot. The slope of experimental plots ranged from 5.5%to 10.2%at an altitude of 125 mand 896 $m^2$ ($28m{\times}32m$) in area. The total respective rainfall events were 47, 52, 52 times during experimental period from 2006 to 2008, while approximately 65 percent of daily rainfall intensity from2006 to 2008 was less than 20 mm a day. The organic matter contents on the surface 15 cm soil ranging from1.23%to 1.84%in 2006 were changed into from1.35 %to 2.28%in 2008 in the order of control > glyphosate > paraquat > bare plot in 2008, indicating that the herbicide treatment influenced the accumulation organic matter in soil. The changes in soil particle contents showed that the loss of soil particles in top 5 cm soil depth was greater in a bare soil than in other treatments such as control, glyphosate, and paraquat-treated plot. The net changes in the bulk densities showed that there were little variations between May of 2006 and Nov. of 2008 even though there were some losses of the soil particles. The soil strength of the glyphosate-treated bare plots was much greater than those of other plots such as control, glyphosate, and paraquat plots. However the soil strengths in control plots were lower than those in the plots of glyphosate and paraquat treated ones.

• Journal of Conservation Science
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• v.26 no.1
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• pp.61-67
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• 2010

After selecting five types of adhesive epoxy resin for metallic cultural assets such as $Araldite^{(R)}$ rapid type, $Devcon^{(R)}$, $Araldite^{(R)}$ SV427+HV427, $CDK^{(R)}$520, $Araldite^{(R)}$ AW106+HV953 which had already been studied, this paper approached more closely the problem of yellowing and the signal of aging with time passing by connecting the problems with the safety of metallic cultural assets. The change of physical properties according to the change of state of epoxy adhesives was investigated through the change of flexural strength and the change of surface hardness by artificially providing the possible environmental change factors such as ultra-violet ray, and acid base, and how the epoxy chemically changes in its ingredients by the environment was analyzed through FT-IR. As a result of the experiment, for the most part of adhesives brought about the physical change of flexural strength, the change of surface hardness, and the chemical change of chemical ingredients as the product of alcohol, which were respectively different according to the time of ultraviolet irradiation, and acid base change. Under most of the conditions, SV427+HV427 and $CDK^{(R)}$520 were fairly stabilized under each condition of weatherability, but it seems that they should be refrained from being applied in case that the area to restore is thin and wide because the degree of flexural strength of themselves is low. Also, it is found that the preservation environment is very important not only for artifacts but also for the preservation of resins sused for preservation treatment.

• Journal of Adhesion and Interface
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• v.11 no.1
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• pp.15-25
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• 2010

In the present study, isothermal stabilization processes for rayon fabrics were performed at two relatively low temperatures $180^{\circ}C$ and $200^{\circ}C$ for a long period of time. The results of weight loss, dimensional shrinkage, X-ray diffraction and scanning electron microscopic observations studied with the rayon fabrics before and after the isothermal stabilization indicated that the chemical and physical changes of rayon precursor fibers proceeded continuously and slowly at the stabilization temperature below $200^{\circ}C$. And the pre-treatment with four different chemical compounds done prior to stabilization process influenced differently the characteristics of rayon fabrics. As a result, it was noticed that under the given stabilization conditions, $H_3PO_4$ and $Na_3PO_4$ played a role in catalyzing the stabilization reaction of rayon fabric whereas $NH_4Cl$ and $ZnCl_2$ played a role in delaying or retarding the reaction. $H_3PO_4$ showed the lowest percent weight loss of the fabric in the second stabilization conducted at $350^{\circ}C$. It was considered that phosphoric acid, which has a function of flame retardant, contributed to retarding somewhat the subsequent reaction even in the second stabilization step.

• Journal of Conservation Science
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• v.34 no.5
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• pp.345-358
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• 2018

The purpose of this study is to analyze the characteristics of low-grade 12th-century celadons, which were excavated from a kiln site in Noksan-dong, Busan. The physical and chemical properties of the body and the glaze are evaluated through scientific analyses. All the selected celadon shards have a similar body color, regardless of the kiln from which they originated. The celadon shards from 2 3 kilns are brighter than those from 4 5 kilns, and there are two saturations, namely gray and brown. The brightness of the glaze shows a high contribution of red and yellow. The porosity of the selected shards is 8.8% in the gray saturation and 16.1% in the brown saturation. The major chemical compositions of the body and glaze are in the typical chemical composition of the celadon, but the $TiO_2$ flux contents are different. The visible characteristic difference between the 2 3 kilns and the 4 5 kilns can be attributed to the mixing and the firing process rather than the raw materials used. The difference in the $Fe_2O_3$ and $K_2O$ flux between the 2 3 and 4 5 kilns can be attributed to changes in the ingredient combination during the process. In conclusion, Noksan-dong celadon could not be easier vitrification due to the manufacturing process that primary burning process, It is highly likely that there were process differences in kilns to produce high quality celadon.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.53-58
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• 2015

Polycarbonate (PC)/graphene oxide (GO) composites with 3 phr of GO were prepared by using a twin screw extruder at 240, 260, and $280^{\circ}C$ after mixing the solution with chloroform. It was confirmed by DSC and TGA that the glass transition temperature ($T_g$) of PC/GO composites were not changed and the thermal stability was the best in case of the extrusion temperature at $260^{\circ}C$. Thermo mechanical properties of PC/GO composites according to extrusion temperatures were measured by dynamic mechanical analysis (DMA). Storage moduli of PC/GO composites were higher than that of pure PC and there was no detectable changes at varying the extrusion temperature. Based on these results, the extrusion temperature of PC/GO composites was fixed at $260^{\circ}C$. The degree of the chemical reaction of PC/GO composites with respect to the GO reduction time was confirmed by the C-H stretching peak at $3000cm^{-1}$ and the degree of the chemical reaction was similar to that of GO when the reduction time was 1 h. A decrease in the complex viscosity as a function of the GO reduction time was detected by dynamic rheometer, which may be originated from the enhancement of GO dispersion by PC-GO reaction. The GO dispersion was confirmed by scanning electron microscope (SEM).

• Journal of dental hygiene science
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• v.8 no.4
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• pp.255-260
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• 2008

The purposes of this study were to examine the effect of 35% hydrogen peroxide (HP) bleaching agent on the changes in physical and chemical characteristics of tooth. The bleached teeth showed an apparent color changes. The whiteness increased linearly within the tested period as the period of bleaching increased. The microhardness between bleached groups after bleaching showed any statistically significant difference according to the paried t-test. The bleached enamel surface showed any apparent morphological changes compared to the enamel which was stored in distilled water only. The difference of the total mineral contents for the distilled water and hydrogen peroxide did not show statistical significance. These results demonstrated that bleaching using 35% hydrogen peroxide were adversely affects application time of experimental group and may confirm the safety of using these agents for a short time in dentist-monitored bleaching.

• Journal of the Korean GEO-environmental Society
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• v.18 no.1
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• pp.23-29
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• 2017

This study, to provide quantitative data related to compaction characteristics, identifies the compaction characteristics of various types of soil samplers, in relation to their particle-size distribution and plasticity degree, and the compaction characteristics of artificially created granular materials, in relation to their A & D compaction. The results of the experiments show as follows. $r_{dmax}$ of clay is less than those of both sand and gravel approximately by 10%. O.M.C of clay has turned out to be greater than sand and gravel approximately by 20% and 30%, respectively. Changes in the compaction characteristics can be observed clearly around 30~60% of sand and 30~50% of passing No.200 sieve. It has also been shown that the compaction characteristics related to LL and PL are similar to each other in changes, and that the compaction characteristics become less clear with higher percent of fine grained soil. The compaction characteristics of the artificially created granular materials and field materials have appeared almost similar to each other. $r_{dmax}$ is less approximately by 30% and O.M.C greater approximately by 20% in A compaction than in D compaction. As $r_{dmax}$ and O.M.C become greater, its rate increases.