• Korean Journal of Medicinal Crop Science
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• v.26 no.4
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• pp.317-327
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• 2018

Background: The root of Angelica gigas Nakai is used as a traditional herbal medicine in Korea for the treatment of many diseases. However, the poor water solubility of the active components in A. gigas Nakai is a major obstacle to its bioavailability. Methods and Results: This work aimed at enhancing the solubility of the active compounds of A. gigas Nakai by a chemical (using a surfactant) and physical (hot melt extrusion, HME) crosslinking method. Fourier transform infrared spectroscopy revealed multiple peaks in the case of the extrudate solids, attributable to new functional groups including carboxylic acid, alkynes, and benzene derivatives. Differential scanning calorimetry analysis showed that the extrudate soilid had a lower glass transition temperature ($T_g$) and enthalpy (${\Delta}H$) ($T_g:43^{\circ}C$, ${\Delta}H$ : < 6 J/g) as compared to the non-extrudate ($T_g:68.5^{\circ}C$, ${\Delta}H:123.2$) formulations. X-ray powder diffraction analysis revealed the amorphization of crystalline materials in the extrudate solid. In addition, enhanced solubility (53%), nanonization (403 nm), and a higher amount of extracted phenolic compounds were achieved in the extrudate solid than in the non-extrudate (solubility : 36%, nanonization : 1,499 nm) formulation. Among the different extrudates, acetic acid and span 80 mediated formulations showed superior extractions efficiency. Conclusions: HME successfully enhanced the production of amorphous nano dispersions of phenolic compound including decursin from extrudate solid formulations.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.199-204
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• 2016

The adsorption of Rhodamine-B dye using granular activated carbon from aqueous solution was investigated. Adsorption experiments were carried out as a function of the adsorbent dose, pH initial concentration, contact time and temperature. The equilibrium adsorption data showed a good fit to Langmuir isotherm model. Based on the estimated Langmuir separation factor ($R_L$ = 0.0164~0.0314), our adsorption process could be employed as an effective treatment method. The kinetics of adsorption followed the pseudo first order model. Also, the negative values of Gibbs free energy (-4.51~-13.44 kJ/mol) and positive enthalpy (128.97 kJ/mol) indicated that the adsorption was spontaneous and endothermic process. The isosteric heat of adsorption increased with increase in the surface loading indicating lateral interactions between the adsorbed dye molecules.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.4
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• pp.685-690
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• 2008

In numerically evaluating the thermal performance of the heat exchanger, numerical values of thermodynamic properties such as temperature, pressure, specific volume, enthalpy and entropy are required. But the steam table or diagram itself cannot be directly used without modelling. In this study the applicability of neural networks in modelling superheated water vapor was examined. The multi-layer neural networks consist of an input layer with 2 nodes, two hidden layers with 15 and 25 nodes respectively and an output layer with 3 nodes. Quadratic spline interpolation was also applied for comparison. Neural networks model revealed smaller percentage error compared with spline interpolation. From this result, it is confirmed that the neural networks could be a powerful method in modelling the superheated water vapor.

• Journal of the Korean Society of Mineral and Energy Resources Engineers
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• v.55 no.6
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• pp.670-687
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• 2018

This paper reviews the structures, physical and chemical properties, origins and global distribution, amount of energy resources, production technologies, and environmental impacts of gas hydrates to understand the gas hydrates as future energy sources. Hydrate structures should be studied to clarify the fundamentals of natural gas hydrates, hydrate distributions, and amount of energy sources in hydrates. Phase equilibria, dissociation enthalpy, thermal conductivity, specific heat, thermal diffusivity, and fluid permeability of gas hydrate systems are important parameters for the the efficient recovery of natural gas from hydrate reservoirs. Depressurization, thermal stimulation, inhibitor injection, and chemical exchange methods can be considered as future technologies to recover the energy sources from natural gas hydrates, but so far depressurization is the only method to have been applied in test productions of both onshore and offshore hydrates. Finally, we discuss the hypotheses of environmental impacts of gas hydrates and their contribution to global warming due to hydrate dissociation.

• Journal of the Korean Chemical Society
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• v.17 no.3
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• pp.145-153
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• 1973

The temperature effects on the equilibria between polymolybdatd anions in 1M sodium perchlorate solution has been investigated in the temperature range of 20~50$^{\circ}$C. The polymolybdate anions formed are heptamolybdate ($Mo_7O_{24}^{6-}$) ions and the protonized forms of heptamolybdate ions ($H_LMo_7O_{24}^{(6-L)-}$). The equilibrium constants for the formation of heptamolybdate ions calculated by Sillen's method are as follow;$8H^{+}+7MoO_4^{2-}=Mo_7O_{24}^{6-}+4H_2O$, $k_{7.8}=2.77{\times}10^{53}:20^{\circ}C= 9.29{\times}10^{51}:40^{\circ}C$,$k_{7.8}= 4.22{\times}10^{52}:30^{\circ}C = 9.29{\times}10^{51}:50^{\circ}C$ The enthalpy change for calculated for the above reaction is 31.51 kcal/mole. A method of calculation of the equilibrium constants for the formation of protonized heptamolybdate ions from heptamolybdate ions and hydrogen ions has been derived. The equilibrium constants calculated for the formation of protonized heptamolybdate ions are as follow; $ LH^++ Mo_7O_{24}^{-6} = H_LMo_7O_{24}^{(6-L)-} : L = 1\;or\;2$, $k_1 = 2.31{\times}10^4=2.53{\times}10^4=2.76{\times}10^4= 3.10{\times}10^4$, $k_2 = 6.19{\times}10^7\;20^{\circ}C = 7.80{\times}10^7\;30^{\circ}C = 1.22{\times}10^8\;40^{\circ}C = 2.03{\times}10^8\;50^{\circ}C$The enthalpy change for the following step reactions are as follow;$H^{+}+Mo_7O_{24}^{6-}= HMo_7O_{24}^{5-}\;{\Delta}H^{\circ}=1.90 kcal/mole$, $2H^{+}+Mo_7O_{24}^{6-}=H_2Mo_7O_{24}^{4-}\;{\Delta}H^{\circ}=7.50kcal/mole$

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.3
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• pp.366-372
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• 2006

This study is to investigate the physicochemical properties of differently pretreated chestnut starches during starch isolation and to examine their gelatinization properties by both heat and alkali treatments. One kind is starch A made by alkali method from peeled chestnut. The other is starch B made from chestnut with the outer layer. The results are as follows. Starch A has higher water binding capacity of 86.9% than starch B with 80.66%. Swelling powers of both starch A and B increased rapidly from $60^{\circ}C\;to\;80^{\circ}C$ in both, and since then it has changed a bit. Both began to show their solubility at $60^{\circ}C$ and increased continuously as the temperature went up. Starch A has higher swelling power and solubility than starch B. In iodine reaction, starch A has higher ${\lambda}max$ and absorbance at ${\lambda}max$ than starch B. X-ray diffraction patterns showed that starch A is type $C_b$ and that starch B is type B. Starch B has higher relative crystallinity of 37.0% than starch A with 36.2%. The results by differential scanning calorimetry revealed that starch A gelatinized from $66.95^{\circ}C$ to $77.5^{\circ}C$ and its enthalpy is 2.04 cal/g. And starch B gelatinized from $67.09^{\circ}C\;to\;77.5^{\circ}C$, and its enthalpy is 2.29 cal/g. Amylograms of chestnut starch at 6.5% concentration indicated that starch B needs higher onset temperature when beginning to gelatinize than starch A does. But starch A shows much higher peak viscosity, breakdown and setback than starch B does. Starch A shows higher viscosity, gel volume, and optical transmittance in gelatinization properties by alkali than starch B does.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.5
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• pp.681-688
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• 1996

To investigate the effort of drying methods on the physicochemical properties of agar, gel strength, viscosity, melting and setting point, and phase transition by differential scanning calorimetery (DSC) during its heating were determined. In addition the structural differences of agar powder by scanning electron microscope (SEM) was examined. The most shortest onset temperature of gel strength increase was extruding method among any other methods. Viscosity of agar with hot air method, 400.00 cps at $45^{\circ}C$, was markedly increased, but with spraying and extruding ones were little change. The melting and setting point, and the temperature for maximum endothermic and enthalpy for agar with extruding one, $80.01^{\circ}C,\;36.05^{\circ}C\;and\;61.72^{\circ}C,\;0.73\;cal/g$, respectively, were lowest among the drying ones. But in the case of reheating after gelling, there were little change in all methods. Observing the surface structure of agar with SEM, extruding method showed the most unstable with absorptive property.

• Journal of the Society of Disaster Information
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• v.19 no.3
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• pp.532-544
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• 2023

Purpose: To identify and evaluate the risk of chemical fire causative substances by using thermal analysis methods (DSC, TGA) for the hazards and physical property changes that occur when newly used biofuels are mixed with existing fuels It is to use it for identification and evaluation of the cause of fire by securing data related to the method and the hazards of the material according to it. Method: The research method used in this experiment is the differential scanning calorimeter (DSC: Difference in heat flux) through quantitative information on the caloric change from the location, shape, number, and area of peaks. flux) was measured, and the weight change caused by decomposition heat at a specific temperature was continuously measured by performing thermogravimetric analyzer (TGA: Thermo- gravimetric Analyzer). Result: First, in the heat flux graph, the boiling point of the material and the intrinsic characteristic value of the material or the energy required for decomposition can be checked. Second, as the content of biodiesel increased, many peaks were identified. Third, it was confirmed through analysis that substances with low expected boiling points were contained. Conclusion: It was shown that the physical risk of the material can be evaluated by using the risk of biodiesel, which is currently used as a new energy source, through various physical and chemical analysis techniques (DSC + TGA).In addition, it is expected that the comparison of differences between test methods and the accumulation and utilization of know-how on experiments in this study will be helpful in future studies on physical properties of hazardous materials and risk assessment of materials.

• Analytical Science and Technology
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• v.10 no.3
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• pp.209-215
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• 1997

Li-AGICs as a anode of secondary battery were synthesized by high-pressure method as a function of the Li-contents. The characteristics of these prepared compounds were determined from the studies with X-ray diffraction method, UV/VIS spectrophotometric and differential scanning calorimeter(DSC) analysis. From the results of X-ray diffraction, it was found that the lower stage intercalation compounds were formed with increase of Li-contents. The mixed stages in these compounds were also observed. In the case of the $Li_{30wt%}$-AGIC, the compounds in the stage 1 structure were formed predominantly, but the structure of only pure stage 1 for structural defect of artificial graphite is not observed. According to UV/VIS spectrophotometric analysis, $Li_{30wt%}$-AGIC shows distinguishable energy state spectrum with the position of $R(%)_{min}$ values, but the characteristic spectra of almost all Li-AGICs are not observed. The enthalpy and entropy changes of the compounds can be obtained from the differential scanning calorimetric analysis results. From the results, it was found that exothermic and endothermic reactions of Li-AGICs are related to thermal stability of lithium between artificial graphite layers.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1143-1152
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• 2019

In order to study the solubilization of aniline by cationic surfactants (DTAB, TTAB and CTAB), the solubilization constant (K_s) and thermodynamic functions were measured and calculated by using the UV-Vis method. The solubilization constants of aniline with the change of temperature were measured, and the effects of addition of ionic salts and organics on the solubilization constants were investigated. These effects of additives and temperature changes were compared and analyzed for each type of surfactant, and the solubilization of aniline was analyzed microscopically by comparing and evaluating the thermodynamic functions obtained from the solubilization constants. As a result, the Gibbs free energy and enthalpy changes were both negative and the entropy changes were positive within the measured range for the solubilization of aniline by cationic surfactants. The solubilization constant value decreased with increasing temperature and increased with increasing carbon chain length of the surfactant. As the concentration of ionic salts increased, the Gibbs free energy change increased at first and then decreased. In n-butanol solution, the Gibbs free energy change tended to increase continuously with increasing the concentration of n-butanol.