• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.19-26
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• 2024

In this study, the electrochemical properties of SiOx@C composite materials were prepared to alleviate volume expansion and cycle stability of silicon and to increase the capacity of anode material for LIBs. SiO₂ particles of 100, 200, and 500 nm were synthesized by the Stӧber method, and reduced to SiOx (0≤x≤2) through the magnesiothermic reduction method. Then, SiOx@C anode materials were synthesized by carbonization of PVC on SiOx. The physical properties of prepared SiOx and SiOx@C anode materials were analyzed by XRD, SEM, TGA, Raman spectroscopy, XPS and BET. The electrochemical properties were investigated by cycling performance, rate performance, CV and EIS test. As a result, the SiOx@C-7030 manufactured by coating carbon at SiOx : C = 70 : 30 on a 100 nm SiOx with the smallest particle size showed the best electrochemical properties with a discharge capacity of 1055 mAh/g and a capacity retention rate of 81.9% at 100 cycles. It was confirmed that cycle stability was impoved by reducing particle size and carbon coating.

• Clean Technology
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• v.30 no.3
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• pp.220-227
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• 2024

As the demand for lithium-ion batteries with high capacity and high energy density has rapidly increased, silicon anodes (theoretical capacity = 3,570 mA h g^-1) have garnered attention as potential replacements for conventional graphite anodes (theoretical capacity = 372 mA h g^-1). However, silicon anodes suffer from severe volume expansion (~360%) during lithiation, low ionic conductivity (10^-14 ~ 10^-13 cm² S^-1), and low electrical conductivity (10^-2 S cm^-1), resulting in poor cycling and rate performance. To address these issues, this study synthesized core@shell-structured silicon@carbon nanoparticles (Si@C NPs) via a one-pot spray pyrolysis process using Pluronic-F127. Pluronic-F127 in the spray solution contributes to the synthesis of nanoparticles by preventing the formation of silicon nanoparticle/dextrin agglomerates and by undergoing pyrolysis simultaneously. Additionally, dextrin derived amorphous carbon was coated on the surface of the silicon nanoparticles to act as an electron transport pathway within the anodes and enhance the electrical contact between the silicon nanoparticles. The Si@C NPs exhibited a discharge capacity of 1,912 mA h g^-1 after 50 cycles at 1.0 A g^-1 and high rate capabilities (discharge capacity of 1,493 mA h g^-1 at 3.0 Ag^-1). The silicon@carbon composite nanoparticle synthesis strategy based on the spray pyrolysis process presented in this study is expected to offer a new direction for improving the performance of silicon anode materials.

• Childhood Kidney Diseases
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• v.6 no.2
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• pp.169-177
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• 2002

Purpose: Hypertension accelerates the progression of chronic renal disease, whether it results from, or causes, the renal disease. Therefore, the control of hypertension is one of the important factors that retard the rate of renal deterioration. We compared the effects of different antihypertensive agents on renal function and glomerular morphology In subtotal nephrectomized rats. Materials and methods: After induction of chronic renal failure with 5/6 nephrectomy, the rats were divided into three groups; control group (Group C), enalapril group (Group E), and nicardipine group (Group N). Systolic blood pressure was measured by tail cuff method every 4 weeks until 12 weeks after nephrectomy. At 12 weeks after nephrectomy, all rats were placed in metabolic cages for 24 hour urine collections to measure urinary protein and creatinine excretion. After urine collection and blood sampling for serum creatinine, all rats were sacrificed. The renal tissue was processed for morphometric study with light microscope and electron microscope. Results: 1. The blood pressure of Group C increased progressively, but both enalapril and nicardipine prevented the development of hypertension, and the two drugs were equally effective in maintaining normal blood pressure throughout the study. 2. Twenty-four hour urinary protein excretion was lower in Group E compared to Group C and Group N 3. Mesangial expansion score in both treated groups were significantly lower than the control group. Mean glomerular volume in Group E was significantly reduced compared to Group C and Group N. There was no significant difference in mean glomerular volume between Group C and Group N. 4. There was no significant difference in podocyte structural changes, estimated by filtration slit length density, among control, enalapril and nicardipine treated groups. Conclusion: Control of hypertension with enalapril or nicardipine afforded considerable protection from mesangial expansion in the rat remnant kidney model. But protein excretion and glomerular growth were significantly reduced in Group E compared to Group N. There was no significant difference in podocyte structural changes among the 3 groups.

• Journal of Korean Society of Forest Science
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• v.37 no.1
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• pp.17-30
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• 1978

Press drying was used on italian poplar (Populus euamericana) to find the profitable means of drying. This study was designed to investigate the process of platen drying considering core temperature, drying time, current moisture content, drying rate, shrinkage and recovery, and green volume specific gravity, equilibrium moisture content and dimensional stability of press dried material and air dried material, The drying tests were conducted using 1.5 centimeter thick material at platen temperature of $175^{\circ}C$. The results were summarized as follows. 1. Core temperature was divided into three stages of drying characterized by period initial heating, plateau temperature and rising core temperature. Plateau temperature was 114 to $119^{\circ}C$. 2. The following predicting equations of drying time(y) in different core temperatures were developed for initial thickness($x_1$), initial moisture content ($x_2$) and final moisture content ($x_3$) 3. The predicting equaltion of current moisture content(u) was log u=4.658-0.060t as funtion of drying time(t) and that of drying rate(r) was log r=-2.797-0.049t. Current moisture content and drying rate of air drying were shown in figure 2. 4. The predicting equation of shrinkage in thickness direction(y) was log y=1.933+0.038t as function of drying time(t), and that of expansion in width direction was $y=-0.692+0.043t-0.001t^2$. 5. Thickness shrinkage was increased more than proportional at to pressure increase. Width shrinkage and thickness recovery was greatest at 35psi. 6. Green volume specific gravity of press dried material was 25% greater than that of air dried material. But equilibrium moisture content of press dried material was less 24% than that of air dried material. Antishrinkage efficiency of press dried material were obtained 27.7%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.7
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• pp.833-840
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• 2017

For wide application of perilla leaf, which has various healthy functions and can be easily cultured across Korea, the physicochemical and sensory properties of pan bread made with various amounts of squeezed perilla leaf juice (SPLJ) were analyzed. When dough characteristics were analyzed by using farinograph, consistency and dough development time were not significantly different between the control and bread dough made with various amounts of SPLJ, whereas dough stability time increased with increasing SPLJ amount. Expansion rate of dough decreased with increasing SPLJ amount. The volume, specific volume, and baking loss rate of pan bread made with various SPLJ amounts decreased with increasing SPLJ amount. Pan bread crumb colors became thickened and greenish with increasing SPLJ amount. For physical properties of pan bread made with various SPLJ amounts, springiness and cohesiveness decreased with increasing SPLJ amount, whereas brittleness, chewiness, and hardness increased with increasing SPLJ amount. In the sensory strength analysis, pore uniformity and soft texture decreased with increasing SPLJ amount, whereas crumb color (dark greenish), perilla leaf odor, perilla leaf taste, and chewing texture increased with increasing SPLJ amount. In the overall acceptance analysis, 1.5% SPLJ was the most preferred with a score of 7.10. However, statistical differences between 1.5% and 1.0% SPLJ were not detected at P<0.05. In the partial least squares analysis, consumers liked bread with a green crumb color, perilla leaf odor, perilla leaf taste, and soft and chewing texture. In conclusion, physicochemical properties of pan bread made with SPLJ were less desirable than those of the control; however, consumer acceptance of pan bread made with 1.5% SPLJ was shown the highest. Therefore, methods for increasing physicochemical properties of pan bread made with SPLJ need to be developed for wide application of perilla leaf.

• Journal of the Korean GEO-environmental Society
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• v.13 no.12
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• pp.5-16
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• 2012

The second scientific antarctic station of South Korea is under construction at Terra Nova Bay located in eastern Antarctica. Ground condition in the Antarctica is frozen in general, but there are seasonal frozen grounds with active layers sporadically. When the active layer is frozen, frost heaving occurs that might cause the differential movement of frozen ground and the failure of structures. Therefore, it is necessary to determine the frost heaving susceptibility of soils at Terra Nova Bay before starting antarctic station construction. This study presents experimental investigation of the frost heaving susceptibility of soil samples with variation of particle sizes and unfrozen water contents. The soil samples were taken from five different locations at Terra Nova Bay and physical properties, unfrozen water content, and frost heaving tests were performed. For the frost heaving tests, soil specimens were frozen with constant freezing temperatures at the top and with drainage at the bottom in order to stimulate the frost heaving. The frost heaving tests provide volume expansion, volumetric strain, and heaving rate which can be used to analyze the relationship between the frost heaving vs. particle size and the frost heaving vs. unfrozen water content. Experimental results show that the more the fine contents exist in soils, the more frost heaving occurs. In addition, the frost heaving depends on unfrozen water content. Experimental data can be used to evaluate the frost heaving susceptibility of soils at the future construction site in the Antarctica.

• Journal of Korea Foresty Energy
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• v.21 no.2
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• pp.51-61
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• 2002

This study was conducted to investigate and compare species composition, stand structure, and growth pattern for two different sites in which silvopastoral system has been taking place. One site was the pasture area where a number of trees were removed and grasses were planted for cattle grazing, and the other site was the deciduous forest that has been established by ecological succession. The results were as follows: 1. Nine tree species were present equally in the pasture area and the deciduous forest. Of these species, seven tree species were growing in common for two sites. However, the species composition, including density and frequency, was varied by sites. 2. The number of stems per hectare in the pasture area was 71, and that in the deciduous forest was 1,433, having shown the big difference. It is estimated that, considering the growth rate, better grown trees were remained at the time of harvesting in 1996. 3. The growth of diameter, height, and basal area in the pasture area was superior to that in the nearby deciduous forest. In spite of higher values of diameter and height, the timber volume of pasture area per unit area was less than 15% of that in the deciduous forest. 4. Providing sufficient growing space, the pasture area supported higher values of diameter and height. The wider growing space also had influence on the expansion of crown of trees by the result of deliquescent growth pattern. From this point of view, more research would be needed to establish appropriate number of trees for silvopastoral system.

• Korean Journal of Construction Engineering and Management
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• v.11 no.6
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• pp.111-121
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• 2010

As the customer's interest for sidewalk block in the street or apartment complex is increasing, the materials of block which had been a concrete block exclusively are varied to clay paver, native rock and wood etc. Especially, the sales volume of clay paver which is environment-friendly and ergonomic is dramatically increasing every year with two digits growth rate, however, many problems like "Edge Cracking" "Freezing Breakage" "Bending Breakage" "Joint Gap" are happening frequently within a couple of hours after installation due to the durabilities. Because of the characteristics of Ceramic products, clay pavers are very easy to be broken when they are bumped against each other. In addition, they are relatively fragile by a freezing expansion breakage when exposed to water due to hydrophilic property as well as the intensity and absorptance of the products are varied with small difference from the production process such as production equipment and process control. Therefore, it costs a lot of money to repair the breakdown unless production and installation is carried out according to the strict criteria of the quality control. In this study, the symptoms of breakdown frequently happened in clay paver are classified by each type and finally the solution for this problem in the production of brick, installation and criteria of quality control through compressive strength and absorptance test is suggested.

• Journal of Korean Society for Geospatial Information Science
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• v.5 no.2 s.10
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• pp.131-144
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• 1997

Traffic jam densified day by day is phenomenon to occur lack of the road capacity in comparison with traffic density, but lack of the road cannot be concluded by main cause of traffic ism. Because the central function of a city would be concentrated upon the downtown and traffic demand would not be evenly distributed by the classification of an hour. Therefore, this study based on the fact that each driver will select the route generating traffic delay very low when path choice from origin to destination in travel plan estimating the quality of passage could be maintained the speed he want will approach to a characteristic grasp of a road, traffic, driver changing every moment by traffic-demand of road increased as a geometrical series with analysis a classification of a street, a intersection along the path on traffic density and highway capacity analysis the path using GIS techniques about complex street network, also will get the path of actual optimum for traffic delay trend creating under various condition the classification per a hour, a day of week and an incident through network such as analysis for traffic generation zone adjacent about street, intersection, afterward will expect the result increasing efficiency of the road-use through a good distribution of traffic by optimum-path choice, accordingly will prepare the scientific, objective, appropriate basis to decide the reasonable time of a road-widen and expansion through section analysis along a rate of traffic volume vs. road capacity.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1197-1202
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• 1998

Organic acids-eggshell calcium salts were prepared to recycle calcium component from discarded egg shells, and the effects of addition of the salts on dough characteristics of raw noodle and physical properties of cooked noodle were also investigated. Based on Farinograms, calcium malate (CM) affected absorption, stability time, and development time more considerably than calcium citrate (CC). Maximum concentrations of both CM and CC with little influence on dough characteristics were found to be 0.1% and 0.4%, respectively. Addition of calcium salts led to reduce the volume expansion rate of cooked noodle and this was more clearly shown in a sample fortified with CM than CC. As for CC, addition of more than 0.6% resulted in rapid increase in springiness which was in a good agreement with sensory evaluation results. Calcium ion concentration of cooked noodle fortified with 0.4% CC was 48 ppm, equivalent to 86 mg of calcium obtained from 200 g of cooked noodle.