• Korean Journal of Materials Research
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• v.3 no.2
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• pp.158-165
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• 1993

Abstract To investigate the effect of underlying Si on the thermal stability of the TiS$i_2$ film, TiS$i_2$ films obtained by the solid-state reaction of the Ti film on as-deposited or on heat-treated poly-silicon and amorphous-silicon were annealed at 90$0^{\circ}C$ for various times. The poly-Si film was evaluated by XRD, SEM and TEM. The thermal stability of the TiS$i_2$ film was evaluated by measuring the sheet resistance and microstructural evolution during furnace annealing. Agglomeration of the TiSi, film occurred more on amorphous-Si than on poly-Si. The thermal stability of the TiS$i_2$ film was improved by annealing poly-Si. The Si layer crystallized from amorphous-Si has an equiaxed structure with the (111) preferred orientation whereas for as-deposited poly-Si has a columnar structure with the (110) orientation. Better thermal stability of the TiS$i_2$ film can be obtained by the higher surface energy of underlying poly-Si.

• Journal of the Korean Geotechnical Society
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• v.27 no.11
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• pp.71-81
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• 2011

Adfreeze bond strength is a primary design parameter, which determines bearing capacity of pile foundation in frozen ground. It is reported that adfreeze bond strength is influenced by various affecting factors like freezing temperature, confining pressure, characteristics of pile surface, soil type, etc. However, several limited researches have been performed to obtain adfreeze bond strength, for past studies considered only few affecting factors such as freezing temperature and type of pile structures. Therefore, there exists a limitation of estimating the design parameter of pile foundation with various factors in frozen ground. In this study, artificial neural network algorithm was involved to predict adfreeze bond strength with various affecting factors. From past five studies, 137 data for various experimental conditions were collected. It was divided by 100 training data and 37 testing data in random manner. Based on the analysis result, it was found that it is necessary to consider various affecting factors for the prediction of adfreeze bond strength and the prediction with artificial neural network algorithm provides enough reliability. In addition, the result of parametric study showed that temperature and pile type are primary affecting factors for adfreeze bond strength. And it was also shown that vertical stress influences only certain temperature zone, and various soil types and loading speeds might cause the change of evolution trend for adfreeze bond strength.

• KSBB Journal
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• v.21 no.2
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• pp.96-102
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• 2006

Recently, it has been known that Hericium erinaceum is a one of the very useful functional materials with great attention in mushroom processing industry. In present study, a liquid culture which was not studied systematically until now, was conducted as a method of cultivation for H. erinaceum, and also examined the characteristics of the liquid culture and conditions of process optimization. A good basal medium was selected through the cultivation of 16 species mushroom media and the optimum condition for medium and cultivation were chosen by response surface method. From these results, the optimum condition of medium for mushroom was 3% glucose, 0.2% yeast extract/peptone(1:1) and 0.1% $KH_2PO_4/MgSO_4$(1:1) and also the optimal culture condition was obtained at inoculum of 13.42%, temperature of $22.3^{\circ}C$ and pH of 5.7. The mycelial dry weight of 9 g/I was obtained under these conditions and this amount was about 1.7 times higher than that which were cultivated in basal medium for 8 days.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.229-239
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• 2018

The purpose of this study was to effectively produce the biosugar from cell wall of lipid extracted microalgae (LEA) by using microwave-assisted pretreatment without enzymatic hydrolysis process. Response surface methodology (RSM) was applied to optimization of microwave-assisted pretreatment conditions for the production of biosugar based on enzyme-free process from LEA. Microwave power (198~702 W), extraction time (39~241 sec), and sulfuric acid (0~1.0 mol) were used as independent variables for central composite design (CCD) in order to predict optimum pretreatment conditions. It was noted that the pretreatment variables that affect the production of glucose (C6) and xylose (C5) significantly have been identified as the microwave power and extraction time. Additionally, the increase in microwave power and time had led to an increase in biosugar production. The superimposed contour plot for maximizing dependent variables showed the maximum C6 (hexose) and C5 (pentose) yields of 92.7 and 74.5% were estimated by the predicted model under pretreatment condition of 700 w, 185.7 sec, and 0.48 mol, and the yields of C6 and C5 were confirmed as 94.2 and 71.8% by experimental validation, respectively. This study showed that microwave-assisted pretreatment under low temperature below $100^{\circ}C$ with short pretreatment time was verified to be an effective enzyme free pretreatment process for the production of biosugar from LEA compared to conventional pretreatment methods.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.66-72
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• 2018

Corn stover is known as a good candidate for a functional food ingredient when the main lignocellulosic material, lignin, is used as bioactive materials as form of polyphenolic compounds. The purpose of this study was to determine the microwave extraction conditions under which total phenolic compounds (TPC) and flavonoid contents of corn stover were maximized. Microwave-assisted extracts using sulfuric acid ranging from 0 to 1.0 mol with extraction time between 40 and 240 sec were conducted by using response surface methodology (RSM). Microwave power showed significant effects (p<0.05) and the concentrations of TPC and flavonoids increased with increased level of microwave power and extraction time. The optimum conditions for corn stover extraction were determined as 698.6 W, 240 sec, and 0 mol sulfuric acid, and the predicted value of TPC and flavonoid is 82.4 mg GAE/g DM and 18.1 mg/g DM, respectively. Microwave extraction was evaluated as an economic process with low energy consumption, short extraction and high extraction yield of bioactive including TPC and flavonoids compared to conventional extractions.

• Journal of the Korean Ceramic Society
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• v.32 no.5
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• pp.626-634
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• 1995

The SiC-porcelain powder mixtures containing 51.9wt% SiC are produced as by-products from the surface abrasion process of porcelain cores. This raw powders were used as starting materials for the synthesis of SiC containing ceramics. The specimen, which was fired at 135$0^{\circ}C$ from raw powders, had SiC, $Al_{2}O_{3}$, , cristobalite, mullite as crystalline phases, and the fractured microstructure showed dispersed SiC crystalline particles almost wetted with glassy matrix and spherical pores. Although the oxidation of SiC containing powder compacts wetted with glassy matrix and spherical pores. Although the oxidation of SiC containing powder compacts started at the range of 600~80$0^{\circ}C$ form the analysis of weight gain, the presence of $SiO_{2}$ crystallien phase and cristobalite was confirmed at 100$0^{\circ}C$ by XRD analysis. Mullitization of specimens was accelerated by preheating before the final firing. The specimen sintered at 135$0^{\circ}C$ after 100$0^{\circ}C$ preheating consisted of SiC, cristobalite, mullite as crystalline phases, and revealed 2.24g/$cm^{3}$ bulk density, 11.73% water adsorption, porous microstructure with small amount of glassy phase. SiC contents of specimens, which was 51.9 wt% in the raw powders, reduced to 37~22 wt% after firing at 135$0^{\circ}C$ depending on the preheating condition.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.3
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• pp.417-422
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• 2002

Salting conditions on organoleptic properties and rheology of Chinese cabbage were optimized and monitored by four-dimensional response surface methodology. Experimental conditions were decided in the ranges of salt concentration 8∼12%, salting time 5∼25 hr and salting temperature 5∼15$^{\circ}C$. The salted Chinese cabbage with experiment design was measured on organoleptic and physical properties. The organoleptic form of the salted Chinese cabbage showed maximum score in 11.28% of salt concentration, 9.75 hr of salting time and 12.81$^{\circ}C$ of salting temperature. The organoleptic taste was maximized in 11.19% of salt concentration, 11.38 hr of salting time and 13.58$^{\circ}C$ of salting temperature. The organoleptic mouth-feel was maximized in 11.24% of salt concentration, 11.71 hr of salting time and 13.57$^{\circ}C$ of salting temperature. The organoleptic palatability was maximized in 11.52% of salt concentration, 12.86 hr of salting time and 13.07$^{\circ}C$ of salting temperature. In rheological properties of salted Chinese cabbage, hardness and chewiness decreased with the increase of salt concentration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7754-7760
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• 2015

The outer tie rod is one of the part of steering system, the optimization process was executed to find the lightweight design. The inner tie rod was considered in the optimum design of an outer tie rod. it could be closer to the test condition than in the case of considering outer tie rod only. The aluminum forging material was considered as a weight reduction proposal. The target of optimization was the shape of the minimum weight to resist at the load of buckling. RSM and Kriging interpolation method were applied as a optimization method to consider the nonlinear shape optimization problem. Then, 16.3%, 16.6% of weight reduction was obtained from the result comparing with that of the initial model. The results of meta model optimization was compared with that of finite element method. The error values of buckling load estimation were 2.6%, 2.04%. and those of weight estimation were 0.17%, 0.13%. Therefore, it seemed that the result of Kriging model could be obtained closer to optimum value than that of RSM model.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.571-576
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• 2007

Manganese-Coated Sand(MCS) prepared with three different methods were applied in the treatment of soluble $Mn^{2+}$ in batch and column experiments. In the bench-scale MCS preparation, the coating efficiency of manganese on the surface of sand increased as the dosage of initial Mn(II) increased. The removed amount of the soluble $Mn^{2+}$ by MCS increased as the solution pH increased, following a typical anionic-type adsorption. The removed amounts of the soluble $Mn^{2+}$ through adsorption was quite similar over the entire pH range, without depending on the contents of Mn on the surface of sand as well as coating methods. When NaClO was used an oxidant, the removed amount of the soluble $Mn^{2+}$ by MCS increased as the concentration of NaClO increased, This trend might be explained by the increased removal efficiency through coating of manganese oxides produced from oxidation of the soluble $Mn^{2+}$ by NaClO on the surface of MCS. From the bench-scale column experiments, the breakthrough of $Mn^{2+}$ occurred after 4,100 bed volume without presence of NaClO while 1.6-times delayed breakthrough of $Mn^{2+}$ was observed in the presence of NaClO. This result also supports that the removal efficiency of the soluble $Mn^{2+}$ could be enhanced by using NaClO.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.479-486
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• 2009

In natural environments, manganese (Mn) exists in the valence of +2, +3, and +4 and plays a pivotal role as a strong oxidant or reductant in the geochemical cycles of elements. Especially, Mn forms varying (oxyhydr)oxides. The oxidation state of structural Mn is characteristic to each oxide and is one of the most important factors controlling its geochemical behaviors such as solubility, sorption capacity, and redox potential. Therefore, it is important to elucidate processes governing Mn oxidation state in predicting the fate and transport of many redox sensitive elements in the environment. X-ray photoelectron spectroscopy (XPS) is a very useful method to determine the oxidation state of various elements in solid phases. In this study, the oxidation states of structural Mn in MnO, $Mn_2O_3$, $MnO_2$ were assessed based on the binding energy spectra of $Mn2p_{3/2}$ and Mn3s using XPS and were compared with those reported elsewhere. $Mn2p_{3/2}$ binding energies were determined as 640.9, 641.5, 641.8 eV for MnO, $Mn_2O_3$, $MnO_2$, respectively, which indicates that the binding energy increased with increasing Mn oxidation state. It was also noted that Ar etching may cause changes in electronic structure configuration on surface of the original sample.