• Korean Journal of Food Science and Technology
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• v.16 no.4
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• pp.451-456
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• 1984

Rheological properties of gelatinized rice starch solutions were investigated with Brookfield rotational viscometer. The 8% starch solution showed thixotropic behavior with yield stress. The alkali gelatinized starch was more thixotropic than the thermal gelatinized one. The time dependent characteristics of starch solutions followed Tiu's model. The value of rate constant $(a_1)$ in Tiu's model increased linearly with shear rate, and was exponentially dependent on concentration and temperature. Temperature dependency of rate constant and apparent viscosity followed Arrhenius type equation and the activation energy were about 14.3 and 6.8 Kcal/g mole, respectively. The $a_1-value$ was found to be useful to evaluate changes in structaral decay on the shearing time of gelatinized rice starch solutions.

• Korean Journal of Materials Research
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• v.22 no.5
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• pp.243-248
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• 2012

ZrN nanoparticles were prepared by an exothermic reduction of $ZrCl_4$ with $NaN_3$ in the presence of NaCl flux in a nitrogen atmosphere. Using a solid-state combustion approach, we have demonstrated that the zirconium nitride nanoparticles synthesis process can be completed in only several minutes compared with a few hours for previous synthesis approaches. The chemistry of the combustion process is not complex and is based on a metathesis reaction between $ZrCl_4$ and $NaN_3$. Because of the low melting and boiling points of the raw materials it was possible to synthesize the ZrN phase at low combustion temperatures. It was shown that the combustion temperature and the size of the particles can be readily controlled by tuning the concentration of the NaCl flux. The results show that an increase in the NaCl concentration (from 2 to 13 M) results in a temperature decrease from 1280 to $750^{\circ}C$. ZrN nanoparticles have a high surface area (50-70 $m^2/g$), narrow pore size distribution, and nano-particle size between 10 and 30 nm. The activation energy, which can be extracted from the experimental combustion temperature data, is: E = 20 kcal/mol. The method reported here is self-sustaining, rapid, and can be scaled up for a large scale production of a transition metal nitride nanoparticle system (TiN, TaN, HfN, etc.) with suitable halide salts and alkali metal azide.

• Applied Biological Chemistry
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• v.3
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• pp.1-7
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• 1962

In order to study the rate control step in the protein metabolic course of the chlorophyll formation, the transaminase activities which are obtained freely in the extracts of cotyledons of germinating peas at the light and the dark places, are measured in Beckman mopel D.U, spectrophoto meter at 490 mu. In this case, of two enzymatic reaction products; oxalacetic acid and pyruvic acid, the former is converted to pyruvic acid by aniline citrate and after each pyruvate phenyl hydrazones are extracted by toluenes: when this is treated with strong alcoholic alkali, a colored hydrazone is formed and it is measured by above apparatus. The estimated G.O.T. and G.P.T. in the germinated cotyledons at dark and light places considerably differ in their activities; G.O.T. and G.P.T. activities which are formed at the light are more increased than at the dark and also they differ in their rates through germination, though G.O.T. activity increment is smoothly but that of G.P.T. is more sharply, and they are considered to be directly affected to the chlorophyll formation and indirectly to the growth. G.O.T. and G.P.T. in each fractions of cell in the cotyledons should be formed by dissociation of zymogens in the microsomal fractions and it seems to promoted by light. In the formation of the chlorophyll, the protein metabolism occurred mainly in the microsomal fractions and the rate determining step is found at the point where the zymogene that is able to produce G.P.T. is activated, and this activation is promoted by light as noted above.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.575-580
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• 2012

Geopolymers were synthesized using raw materials produced from two different areas: one was from Indonesia and the other was from Habcheon, Korea. The constituting phases of the Indonesian raw material were quartz and kaolinite, while those of the Habcheon sample were quartz, halloysite and albite. They were both calcined at $750^{\circ}C$ for 6 hours, and solution of NaOH and water glass was added to activate the geopolymeric reaction. The compressive strength of geopolymer synthesized from the Indonesian raw material showed a low value of $151\;kgf/cm^2$ after curing for 28 days. However, it could be greatly increased by adding blast furnace slag powders of $1188\;kgf/cm^2$ and $1969\;kgf/cm^2$ at 20 wt% and 40 wt% additions, respectively. The compressive strength of the geopolymer synthesized from the Habcheon raw material was high, at $557\;kgf/cm^2$, after 28 days, and the very high early-stage (3 days) strength of $556\;kgf/cm^2$ for this sample was remarkable. Commercially available Habcheon metastate raw material, of which composition showed low CaO and $Na_2O$ contents compared to the calcined Habcheon raw material, was also examined. It was found that the compressive strength of the commercial metastate type was nearly identical to that of the calcined Habcheon raw material except for the relatively low value at an early curing stage and at a high curing temperature of $60^{\circ}C$.

• Resources Recycling
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• v.22 no.3
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• pp.36-42
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• 2013

According to the recent community-based structures enlargement, specification, and diversification. It needs appropriate construction materials in terms of intensity and environmental aspects. Thus, in manufacturing the cement using micro limestone powder which is main material. It is also expected to save energies and reduces $CO_2$, by using the blast furnace slag and fly ash which are mitigated environmental load construction materials that emerged. In this research, The durability aspect tries to be grasped considering the chemical property according to the coherence of the hydration product. Consequently, The compressive strength was measured over 30 Mpa on 3rd. In addition, according to the content of the limestone powder, the setting time is promoted. It has the feature expanded in the length change. And it is determined because the possibility of replacing the existing for construction material such as it is measured compared with the time to use the portland cement usually that flexural strength is high with the age 7 days ago, so it is sufficient.

• Journal of Soil and Groundwater Environment
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• v.21 no.2
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• pp.29-37
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• 2016

CO₂ injection well sealant is vulnerable to supercritical CO₂ (scCO₂) exposure. To develop an alternative to the conventional sealant system (class G cement/class F fly ash), the performance of slag cement (SPC) systems containing class F fly ash (FFA) or class C fly ash (CFA) was evaluated and compared with the conventional sealant under scCO₂ conditions. All sealant systems showed an immediate increase in compressive strength upon scCO₂ exposure and, at 37.6 MPa, SPC/CFA showed the highest compressive strength after 14 days, which was much higher than the 29.8 MPa of the conventional sealant system. Substantial decreases in porosity were observed in all sealant systems, which were partly responsible for the increase in strength. Carbonation reactions led to pH decreases in the tested sealants from 12.5 to 10~11.6. In particular, the greatest decrease in pH in slag cement/class C fly ash probably supported relatively sustainable alkali activation reactions and the integrity of cement hydrates in this system. XRD revealed the presence of CaCO₃ and a decrease in the content of cement hydrates in the tested sealants upon scCO₂ exposure. TGA demonstrated a greater increase of CaCO₃ and calcium-silicate-hydrate phases in SPC/CFA than in the conventional sealant upon scCO₂ exposure.

• Analytical Science and Technology
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• v.37 no.1
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• pp.47-62
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• 2024

Abu Gurdi area is located in the South-eastern Desert of Egypt which considered as volcanic massive sulfide deposits (VMS). The present work aims at investigating the ore mineralogy of Abu Gurdi region in addition to the effectiveness of the hydrometallurgical route for processing these ores using alkaline leaching for the extraction of Zn, Cu, and Pb in the presence of hydrogen peroxide, has been investigated. The factors affecting the efficiency of the alkaline leaching of the used ore including the reagent composition, reagent concentration, leaching temperature, leaching time, and Solid /Liquid ratio, have been investigated. It was noted that the sulfide mineralization consists mainly of chalcopyrite, sphalerite, pyrite, galena and bornite. Gold is detected as rare, disseminated crystals within the gangue minerals. Under supergene conditions, secondary copper minerals (covellite, malachite, chrysocolla and atacamite) were formed. The maximum dissolution efficiencies of Cu, Zn, and Pb at the optimum leaching conditions i.e., 250 g/L NaCO₃ - NaHCO₃ alkali concentration, for 3 hr., at 250 ℃, and 1/5 Solid/liquid (S/L) ratio, were 99.48 %, 96.70 % and 99.11 %, respectively. An apparent activation energy for Zn, Cu and Pb dissolution were 21.599, 21.779 and 23.761 kJ.mol^-1, respectively, which were between those of a typical diffusion-controlled process and a chemical reaction-controlled process. Hence, the diffusion of the solid product layer contributed more than the chemical reaction to control the rate of the leaching process. High pure Cu(OH)₂, Pb(OH)₂, and ZnCl₂ were obtained from the finally obtained leach liquor at the optimum leaching conditions by precipitation at different pH. Finally, highly pure Au metal was separated from the mineralized massive sulfide via using adsorption method.

• Resources Recycling
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• v.17 no.6
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• pp.68-78
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• 2008

Using a Pinus koraiensis and Pinus rigida which are normally being discarded in South Korea, optimal conditions of producing activated carbons have been studied to recycle as a higher value-added product. This study consists of two processes, the production process of charcoals from waste timbers by low temperature pyrolysis and the production process of activated carbons from the charcoals by chemical activation reaction. This paper deals with the production process of activated carbons from the charcoals by chemical activation reaction. As an alkali has been generally used as an activating agent, KOH and NaOH which react well with a carbon were used in this study. As a result of the experiments, it is confirmed that activated carbons made with KOH treatment had superior values in physicochemical properties to NaOH, showing that there was no remain of KOH at the surface of the charcoals while there was $3{\sim}4%$ of NaOH remaining after the experiments. Thus, it is concluded that KOH reacted more actively with a charcoal than NaOH. Moreover, it was also found that values in physicochemical properties when using a Pinus koraiensis are superior to the ones when using a Pinus rigida. The optimal mixing ratio of an activating agent to a charcoal was 400 wt.%. To improve the physicochemical properties, activated carbons were washed out by distilled water after neutralization with SM hydrochloric acid solution. When activated carbons were produced from a Pinus koraiensis in this optimal conditions, value of BET surface area was found to be approx. $2400\;m^2/g$.

• Toxicological Research
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• v.21 no.2
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• pp.107-113
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• 2005

[ $BARODON^{(R)}$ ] is a multi-purpose, high functional alkali solution made by mixing and liquid-ionizing silicon, calcium, sodium, borax, organic carbon chemicals and silver. In this study, we have investigated the apoptotic potential and mechanistic insights of $BARODON^{(R)}$ in human gastric cancer cell line (AGS cells). In MTT assay, $BARODON^{(R)}$ reduced cell viability in AGS cells. Morphological features of apoptosis with marked cytoplasmic vacuolation and appearance of apoptotic peaks in flow cytometry were observed in AGS cells with$BARODON^{(R)}$ treatment. In addition, $BARODON^{(R)}$ induced apoptosis of stomach cancer cell is related to bax up-regulation, caspase 7 protease activation and subsequent cleavage of poly (ADP-ribose) polymerase (PARP). These results suggest that BARODON can induce the apoptosis of AGS cells through modulation of bcl-2 family and the activation of intrinsic caspase cascades, indicating that it is potentially useful as a anti-cancer agent.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.653-662
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• 2015

In general, the coal gasification has to be operated under high temperature ($1300{\sim}1400^{\circ}C$) and pressure (30~40 bar). However, to keep this conditions, it needs unnecessary and excessive energy. In this work, to reduce the temperature of process, alkali catalysts such as $K_2CO_3$ and $Na_2CO_3$ were added into Cyprus coal. We investigated the kinetic of Cyprus char-$CO_2$ gasification. To determine the gasification conditions, the coal (with and without catalysts) gasified with fixed variables (catalyst loading, catalytic effects of $Na_2CO_3$ and $K_2CO_3$, temperatures) by using TGA. When catalysts are added by physical mixing method into Cyprus coal the reaction rate of coal added 7 wt% $Na_2CO_3$ is faster than raw coal for Cyprus char-$CO_2$ gasification. The activation energy of coal added 7 wt% $Na_2CO_3$ was calculated as 63 kJ/mol which was lower than raw char. It indicates that $Na_2CO_3$ can improve the reactivity of char-$CO_2$ gasification.