• 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.

• Journal of Korean Society of Forest Science
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• v.71 no.1
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• pp.14-21
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• 1985

This study was carried out in order to prevent the devaluation of wood itself and wood products causing by anisotropy, hygroscopicity, shrinkage and swelling - properties that wood itself only have, in order to improve utility of wood, by emphasizing the natural beautiful figures of wood, to develop the dimensional stabilization techniques of wood with PEG that it is a cheap, non-toxic and the impregnation treatment is not difficult, on the effects of PEG molecular weights (200, 400, 600, 1000, 1500, 2000, 4000, 6000) and species (Pinus densiflora S. et Z., Larix leptolepis Gordon., Cryptomeria japonica D. Don., Cornus controversa Hemsl., Quercus variabilis Blume., Prunus sargentii Rehder.). The results were as follows; 1) PEG loading showed the maximum value (137.22%, Pinus densiflora, in PEG 400), the others showed that relatively slow decrease. The lower specific gravity, the more polymer loading. 2) Bulking coefficient didn't particularly show the correlation with specific gravity, for the most part, indicated the maximum values in PEG 600, except that the bulking coefficient of Quercus variabilis distributed between the range of 12-18% in PEG 400-2000. In general, the bulking coefficient of hardwood was higher than that of softwood. 3) Although there was more or less an exception according to species, volumetric swelling reduction was the greatest in PEG 400. That is, its value of Cryptomeria japonica was the greatest value with 95.0%, the others indicated more than 80% except for Prunus sargentii, while volumetric swelling reduction was decreased less than 70% as the molecular weight increase more than 1000. 4) The relative effectiveness of hardwood with high specific gravity was outstandingly higher than softwood. In general, the relative effectiveness of low molecular weight PEG was superior to those of high molecular weight PEG except that Quercus variabilis showed more than 1.6 to the total molecular weight range, while it was no significant difference as the molecular weight increase more than 4000. 5) According to the analysis of the results mentioned above, the dimensional stabilization of hardwood was more effective than softwood. Although volumetric swelling reduction was the greatest at a molecular weight of 400. In the view of polymer loading, bulking coefficiency reduction of swelling and relative effectiveness, it is desirable to use the mixture of PEG of molecular weight in the range of 200-1500. To practical use, it is recommended to study about the effects on the mixed ratio on the bulking coefficient, reduction of swelling and relative effectiveness.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.28-37
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• 2004

A two-dimensional direct numerical simulation was performed to investigate the evolution and vortical structure of a single vortex in reacting and non-reacting jet flow fields. A predictor-corrector-type numerical scheme with a low Mach number approximation was used, and a two-step global reaction mechanism was adopted as the combustion model. Through the comparisons of single vortex behaviors in reacting and non-reacting jet flow fields, it was found that the evolution characteristics and vortical structure of the single vortex were significantly influenced by a outer vortex that was generated from the buoyance effect as well as the chemical heat release. Furthermore, it was also identified that the differences of the vortical structure in reacting and non-reacting jet flow fields were mainly attributed to the thermal expansion, Baroclinic torque and buoyance effect.

• Korean Journal of Food Science and Technology
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• v.49 no.2
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• pp.168-172
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• 2017

In this study, the fermentative characteristics of rye sourdough fermented with Omija extract were investigated. The pH and total titratable acidity, numbers of yeast and lactic acid bacteria, and expansion rate were measured. While the pH of Omija rye sourdough decreased from 5.60 to 3.86, the total titratable acidity significantly increased from 2.39 to 8.50 with fermentation time (p<0.05). The numbers of yeast and lactic acid bacteria significantly increased for 18 h of fermentation period (p<0.05). The expansion rate of Omija rye sourdough showed a maximum of 183%, more than 47% more than the highest value of rye sourdough (129%). These results suggest that the application of Omija extract for making sourdough could be a good way to decrease the sanitary risk especially for early stage of sourdough fermentation. In addition, Omija rye sourdough could contribute to improvement of baking quality such as volume increase and flavor improvement of rye bread.

• Parasites, Hosts and Diseases
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• v.33 no.2
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• pp.131-134
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• 1995

When tachyzoites (RH strain) of Toxoplasmo gondii are injected intramuscularly, experimental mice survive up to 7 days, 1-2 days longer than those infected intraperitoneally. We observed sequential histopathological changes in inguinal Iymph nodes after intramuscular injection of tachyzoites to thighs of specific pathogen free (SPF) mice. Initial findings on 1 or 3 days after the injection were reactive germinal centers, distended sinuses and epithelioid cell clusters in cortical and paracortical regions. Later on 5 days after the injection, however, effacement of nodal structure with depletion of cells and focal necrosis were observed . Necrotizing Iymphadenitis in the experimental murine toxoplasmosis suggests the causal relation between T. gondii infection and the human disease.

• Journal of Energy Engineering
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• v.20 no.3
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• pp.178-184
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• 2011

Compressed Air Energy Storage (CAES) is a combination of energy storage and generation by storing compressed air using off-peak power for generation at times of peak demand. In general, both charging and discharging of high-pressure vessel are unsteady processes, where the pressure is varying. These varying conditions result in low efficiencies of compression and expansion. In this paper, a new constant-pressure CAES system to overcome the current problem is proposed. An energy analysis of the system based on the concept of exergy was performed to evaluate the energy density and efficiency of the system in comparison with the conventional CAES system. The new constant-pressure CAES system combined with pumped hydro storage requires the smaller cavern with only half of the storage volume for variable-pressure CAES and has a higher efficiency of system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2846-2851
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• 2012

Effects of ground tire rubber(GTR) and unexpanded $Expancel^{(R)}$ powders on the thermal conducting characteristics of rigid polyurethane foams(PUFs) were studied. Sub-micron sized GTR powders and $Expancel^{(R)}$ powders were used as the foam nucleating agents to improve the thermal insulating properties of the rigid PUFs. As the results, while the thermal conductivities of the GTR filled-PUF samples were increased linearly with GTR contents, those of $Expancel^{(R)}$ filled-PUF samples were decreased a little bit. It was considered from the results that GTR powders might predominantly play a role as the extending fillers. On the other hand, $Expancel^{(R)}$ powders could act as the foam nucleating agents based on the polar surface, showing smaller cell sized PUF with improved insulating characteristics.

• Culinary science and hospitality research
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• v.23 no.2
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• pp.181-188
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• 2017

Aronia is a superberry that contains antioxidants. Due to its nutritional value, it has received much attention and has been widely researched. In this study, the proportion of aronia powder applied to spelt wheat flour was measured with the pH ratio of the additive and respondents' preference was examined for the preferred addition to the additive population. As a result of the acidity measurement, the pH value tended to decrease as the amount of aronia powder was increased. As for the fermentation expansion rate, the volume of the dough added with aronia powder was measured to be slightly smaller than that without addition of aronia powder. Preference of breads with aronia powder added showed higher preference when 6% was added compared to when 3% of aronia powder was added. As a result of preference survey of breads containing aronia powder, the most preference was given to taste when 3% of aronia powder was added. Color, fragrance, and overall acceptance were the most preferred when 6% of aronia powder was added. Based on these results, the optimal mixing ratio of aronia powder to spelt flour bread was selected to be 6% of aronia powder.

• Magazine of the Korea Concrete Institute
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• v.7 no.4
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• pp.149-156
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• 1995

The fracture process zone in concrete is a region ahead of a traction-free crack, in which two major mechanisms, microcracking and bridging, play important roles. The toughness due to bridging is dominant compared to toughness induced by microcracking, so that the bridging is dominani: mechanism governing the fracture process of concrete. Fracture mechanics does work for concrete provided that the fracture process zone is being considered, so that the development of model for the fracture process zone is most important to describe fracture phenomena in concrete. In this paper the bridging zone, which is a part of extended rnacrocrack with stresses transmitted by aggregates in concrete, is modelled by a Dugdale-Barenblatt type model with linear tension-softening curve. Two finite element techniques are shown for the analysis of progressive cracking in concrete based on the discrete crack approach: one with crack element, the other without crack element. The advantage of the technique with crack element is that it dees not need to update the mesh topology to follow the progressive cracking. Numerical results by the techniques are demonstrated.

• Composites Research
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• v.17 no.6
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• pp.37-43
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• 2004

To determine the effect of chain length and chemical structure of linear amine curing agents on thermal and mechanical properties, a standard bifunctional linear DGEBF epoxy resin was cured with EDA and HMDA having amine group at the both ends of main chain in a stoichiometrically equivalent ratio in condition of preliminary and post cure. From this work, the effect of linear amine curing agents on the thermal and mechanical properties is significantly influenced by numbers of carbon atoms of main chain. In contrast, the results show that the DCEBF/EDA system having two carbons had higher values in the thermal stability, density, shrinkage (%), grass transition temperature, tensile modulus and strength, flexural modulus and strength than the DGEBF/HMDA system having six carbons, whereas the DGEBF/EDA cure system had relatively low values in maximum ekothermic temperature, maximum conversion of epoxide, thermal expansion coefficient than the DGEBF/HDMA cure system. These findings indicate that the packing capability (rigid property) in the EDA structure affects the thermal and mechanical properties predominantly. It shows that flexural fracture properties have a close relation to flexural modulus and strength.