• Korean journal of food and cookery science
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• v.12 no.2
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• pp.186-192
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• 1996

Retrogradation of non-waxy rice (NWR) and waxy rice (WR) cakes (45% moisture) stored at 5$^{\circ}C$, $25^{\circ}C$ and -2$0^{\circ}C$ was studied by differential scanning calorimetry (DSC) and enzymatic ($\beta$-amylase-puuulanase) method. With DSC, endotherms did not appear with rice cakes stored at room ($25^{\circ}C$) and deep freezing (-2$0^{\circ}C$) temperatures but did with samples stored at low temperature (5$^{\circ}C$), showing accelerated retrogradation by low temperature. Onset temperature (To) and peak temperature (Tp) did not change under 14 days at 5$^{\circ}C$ but enthalpy values ($\Delta$H) increased rapidly within one day and increased steadily until 5th day of storage, then equilibrated. Higher $\Delta$H were obtained with WR cakes than NWR cakes. It was suggested that more amylopectin recrystallization occured with WR than NWR. Degrees of gelatinization of rice cakes determined by enzymatic method increased in the following order: 5$^{\circ}C$ < $25^{\circ}C$ < -2$0^{\circ}C$. In contrast with DSC results, dogrees of gelatinization of NWR cakes, were relatively lower than that of WR cakes. However, increased retrogradation extents (melting enthalpies) caused reduced enzyme susceptibilities to $\beta$-amylase-pullulanase system, among NWR or WR cakes stored at 5$^{\circ}C$. The degrees of retrogradation of rice cakes stored at 5$^{\circ}C$ were higher than those stored at $25^{\circ}C$ and -2$0^{\circ}C$ without regard to the kind of rice. The higher sensitivity of the enzymatic method was obtained than that of DSC method when the degrees of retrogradation of rice cakes were determined during storage under this experiment conditions.

• Korean journal of food and cookery science
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• v.18 no.5
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• pp.534-542
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• 2002

This study was carried out to determine the effects of various starches (mungbean starch, cowpea starch and corn starch) on the quality characteristics of Omija jelly made of Omija extract. The viscosity of starch suspended in Omija extract and distilled water was measured by using a RVA(Rapid Visco Analyzer), and, color value, syneresis, texture(rupture test and TPA test) and sensory properties of Omija jelly and pure starch jelly were measured. Gelatinization temperature of each starch suspended in Omija extract was higher than that suspended in distilled water, whereas final viscosity of Omija jelly was decreased. Omija extract appeared to retard the gelatinization of starch and recrystallization of gelatinized starch. The viscosity of com starch was lowest among the three types of starch, suggesting thai higher concentration is needed in the use of com starch. The lightness(L) of corn starch gel was the highest among the gels. The syneresis of Omija jelly was lower than that of starch jelly, therefore, Omija extract seemed to be helpful on the stability of starch gel. Rupture properties of Omija jelly was lower than that of starch jelly, whereas the adhesiveness of omija jelly was greater. Omija jelly made of corn starch was less cohesive and more sticky than other gels, and its acceptability was very low. Sensory characteristics of the gel were relatively well correlated with the mechanical characteristics. Overall acceptability of Omija jelly was high in the concentration of 7, 8% of mungbean starch and 8, 9% of cowpea starch. Thus, the optimum concentration of starch for making Omija jelly using mungbean starch was 7, 8% and that using corn starch was 8, 9%.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.603-608
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• 2001

$MO-SiO_2$ (M = Zn, Sn, In, Ag, Ni) binary silica gels were synthesized by sol-gel method and their structural change with the kind of metal ions was characterized by XRD, FT- IR and $^{29}$Si-NMR. Although X-ray analysis showed partial recrystallization of $AgNO_3$ in $Ag-SiO_2$gel, crystalline phase formed by the bonding between metal ion and the silica matrix didn't appear in all $MO-SiO_2$ gels. The FT-IR analysis showed that Zn, Sn and in partially formed Si-O-M bonding in silica matrix and made an shift of absorption peak to by Si-O-Si symmetrical vibration. In addition, $^{29}Si-NMR$ studies showed that Zn, Sn and In didn't affect sol-gel process of silica and were linked with non-bridging oxygen of the linear silica structure, which formed imperfect network because of low temperature sol-gel process. Ag and Ni make a role of catalysis on sol-gel process, resulting in densifying the silica network structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.69-76
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• 2018

This study examined the effect of the heat treatment and alloying elements (B, Ti) on the microstructures and mechanical properties of API J55 steel. The experiments were carried out using various austenization temperatures ($880^{\circ}C$, $910^{\circ}C$, $940^{\circ}C$), cooling methods (water quenching, oil quenching) and tempering temperatures (none, $550^{\circ}C$, $650^{\circ}C$) with J55 and J55+B,Ti steels. The phase diagram and CCT curve were simulated based on the chemical compositions of the J55 and J55+B,Ti steels to predict the microstructures. The results showed that the A1 and A3 temperatures decreased and, as a result, the noses of the ferrite and bainite parts of the CCT curve moved to the right. Various microstructures were formed, namely martensite, bainite, ferrite and pearlite, in accordance with the heat treatment, which had an effect on the hardness, tensile strength and toughness. Martensite was formed after water quenching, but bainite and ferrite appeared after oil quenching with the J55 specimens. On the other hand, martensite was formed, regardless of the cooling method (water quenching, oil quenching), with the J55+B,Ti specimens, because of the improvement of the hardenability caused by the addition of boron. Therefore, the J55+B,Ti specimens exhibited much higher mechanical properties than the J55 specimens, even after the tempering treatment, since the addition of Ti caused fine precipitates to be formed, which inhibited grain growth at the recrystallization temperature.

• Journal of Ginseng Research
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• v.37 no.1
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• pp.124-134
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• 2013

The authentication of the physico-chemical properties of ginsenosides reference materials as well as qualitative and quantitative batch analytical data based on validated analytical procedures is a prerequisite for certifying good manufacturing practice (GMP). Ginsenoside Rb1 and Rg1, representing protopanaxadiol and protopanaxatriol ginsenosides, respectively, are accepted as marker substances in quality control standards worldwide. However, the current analytical methods for these two compounds recommended by Korean, Chinese, European, and Japanese pharmacopoeia do not apply to red ginseng preparations, particularly the extract, because of the relatively low content of the two agents in red ginseng compared to white ginseng. In manufacturing fresh ginseng into red ginseng products, ginseng roots are exposed to a high temperature for many hours, and the naturally occurring ginsenoside Rb1 and Rg1 are converted to artifact ginsenosides such as Rg3, Rg5, Rh1, and Rh2 during the heating process. The analysis of ginsenosides in commercially available ginseng products in Korea led us to propose the inclusion of the (20S)- and (20R)-ginsenoside Rg3, including ginsenoside Rb1 and Rg1, as additional reference materials for ginseng preparations. (20S)- and (20R)-ginsenoside Rg3 were isolated by Diaion HP-20 adsorption chromatography, silica gel flash chromatography, recrystallization, and preparative HPLC. HPLC fractions corresponding to those two ginsenosides were recrystallized in appropriate solvents for the analysis of physico-chemical properties. Documentation of those isolated ginsenosides was achieved according to the method proposed by Gaedcke and Steinhoff. The ginsenosides were subjected to analyses of their general characteristics, identification, purity, content quantification, and mass balance tests. The isolated ginsenosides showed 100% purity when determined by the three HPLC systems. Also, the water content was found to be 0.534% for (20S)-Rg3 and 0.920% for (20R)-Rg3, meaning that the net mass balances for (20S)-Rg3 and (20R)-Rg3 were 99.466% and 99.080%, respectively. From these results, we could assess and propose a full spectrum of physico-chemical properties of (20S)- and (20R)-ginsenoside Rg3 as standard reference materials for GMP-based quality control.

• Journal of the Korean Magnetics Society
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• v.6 no.4
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• pp.242-250
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• 1996

The effects of annealing in magnetic field after deposition on electromagnetic properties of $Ni_{81}Fe_{19}$ thin($400\;{\AA}$) films prepared by RF-magnetron sputtering were investigated in terms of microstructure and surface morphology. The coercivity of the films was decreased below $300^{\circ}C$ due to stress relief and recrystallization, while increased at $400^{\circ}C$ due to grain growth and increasing the surface roughness. And then, $4{\pi}M_{s}$, was almost independent of annealing temperatures. Increasing the annealing temperature. the electrical resistivity of films was decreased from $37\;{\mu}{\Omega}cm$ to $24\;{\mu}{\Omega}cm$, the magnetoresistance was nearly a constant of about $0.6\;{\mu}{\Omega}cm$, and the MR ratio was increased from 1.5 % to 3.1 %. Therefore, It was shown that increasing the magnetoresistive ratio was mainly affected by decreasing the electrical resistivity. Considering the practical application of the films for magnetoresistive heads, optimal annealing conditions was obtained after one hour annealing at $300^{\circ}C$ in 400 Oe unidirectional magnetic field.

• Economic and Environmental Geology
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• v.28 no.6
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• pp.635-646
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• 1995

Mineralized zone in the Dongyang talc deposits occurs on the lowest dolomite member of the Hyangsanri Dolomite belonging to the Ogcheon Supergroup. Ore bodies are emplaced as pipe-like body along the axis of minor folds plunging $40^{\circ}$ to the west developed in these dolomite layers. Amphibolite and chlorite schist are found along the upper or lower contact of all ore bodies (Kim et al., 1963; Park and Kim, 1966). Following the recrystallization and silicification of dolomite, tremolite and tabular and leafy talc(I) of the earlier stage formed, and microcrystalline talc(II) formed in the later stage. Talc(l) and tremolite formed by the reaction between dolomite and the fluid. Whereas talc (II) formed by the reaction between dolomite and fluid, or by the reaction between early formed tremolite and fluid. During the early stage of mineralization, the fluid was the $H_2O-CO_2$ system dominant in $CO_2$, In the later stage, the composition of the fluid changed to $H_2O-NaCl-CO_2$system, and finally to the $H_2O-NaCl$ system. The pressure and temperature conditions of the formation of tremolite associated with talc(I) were 1,640~2,530 bar, and $440{\sim}480^{\circ}C$, respectively. The pressure and temperature condition of talc(II) ore formation was 1,400~2,200 bar, and $360{\sim}390^{\circ}C$, respectively. These conditions are much lower than the metamorphic pressure and temperature of the rocks from the Munjuri Formation located about 5 km to the noJ:th of Dongyang talc deposit ${\delta}^{13}C$ and ${\delta}^{18}O$ values of dolomite which is the host rock of the talc ore deposit are 2.9~5.7‰ (PDB), and -7.4~l6.8‰ (PDB), respectively. These values are little higher than those from the Cambro-Ordovician limestones of the Taebaeksan region, but belong to the range of the unaltered sedimentary dolomite. ${\delta}^{18}O$and ${\delta}D$ values of the talc from Dongyang deposit are 8.6~15.8‰ (vs SMOW), and -65~-90‰ (vs SMOW), respectively, belonging to the range of magmatic origin. These values are quite different from those measured in the metamorphic rocks of Munjuri and Kyemyungsan Formation. ${\delta}^{34}S$ value of anhydrite is 22.4‰ (CDT), which is much lower than ${\delta}^{34}S$ (30‰ vs COT) of sulfate of early Paleozoic period, and indicates the possibility of the addition of magmatic sulfur to the system. Talc ores show the textures of weak foliation and well developed crenulation cleavages. Talc ore deposit in the area is concluded as hydrothermal replacement deposit formed before the latest phase of the deformations that Ogcheon Belt has undergone.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.233-245
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• 2021

Many studies on the microstructures in rocks have been conducted using experimental methods with various equipment as well as natural rock studies to see the development of microstructures and understand their mechanisms. Grain boundary migration of mineral aggregates in rocks could cause grain growth or grain size changes during metamorphism or deformation as one of the main recrystallization mechanisms. This study suggests improved ways regarding the analog material experiments with reformed equipment to see sequential observations of these grain boundary migration. It can be more efficient than the existing techniques and carry out an appropriate microstructure analysis. This reformed equipment was implemented to enable optical manipulation by mounting polarizing plates capable of rotating operation on a stereoscopic microscope and a deformation rig capable of experimenting with analog materials. The equipment can automatically control the temperature and strain rate of the deformation rig by microcontrollers and programming and can take digital photomicrographs with constant time intervals during the experiment to observe any microstructure changes. The composite images synthesized using images by rotated polarizing plates enable us to see more accurate grain boundaries. As a rock analog material, norcamphor(C7H10O) was used, which has similar birefringence to quartz. Static grain growth and simple shear deformation experiments were performed using the norcamphor to verify the effectiveness of the equipment. The static grain growth experiments showed the characteristics of typical grain growth behavior. The number of grains decreases and the average grain size increases over time. These case experiments also showed a clear difference between the growth curves with three temperature conditions. The result of the simple shear deformation experiment under the medium temperature-low strain rate showed no significant change in the average grain size but presented the increased elongation of grain shapes in the direction of about 53° regarding the direction perpendicular to the shearing direction as the shear strain increases over time. These microstructures are interpreted as both the plastic deformation and the internal recovery process in grains are balanced by the deformation under the given experimental conditions. These experiments using the reformed equipment represent the ability to sequentially observe changing the microstructure during experiments as desired in the tests with the analog material during the entire process.

• The Journal of the Petrological Society of Korea
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• v.18 no.3
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• pp.223-236
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• 2009

Ultramafic xenoliths from southeastern part of Jeju Island can be grouped into two types: Type I and Type II. Type I xenoliths are magnesian and olivine-rich peridotite (mg#=89-91), which are commonly found at the outcrop. Most previous works have been focused on Type I xenoliths. Type II xenoliths, consisting of olivine, orthopyroxene and clinopyroxene with higher Fe and Ti components (mg#=77-83) and lower Mg, Ni, Cr, are reported in this study. They are less common with a more extensive compositional range. The studied Type II xenoliths are wehrlite, olivine-clinopyroxenite, olivine websterite, and websterite. They sometimes show ophitic textures in outcrops indicating cumulate natures. The textural characteristics, such as kink banding and more straight grain boundaries with triple junctions, are interpreted as the result of recrystallization and annealing. Large pyroxene grains have exsolution textures and show almost the same major compositions as small exsolution-free pyroxenes. Although the exsolution texture indicates a previous high-temperature history, all mineral phases are completely reequilibrated to some lower temperature. Orthopyroxenes replacing clinopyroxene margin or olivine indicate an orthopyroxene enrichment event. Mineral phases of Type II are compared with Type I xenoliths, gabbroic xenoliths, and the host basalts. Those from Type II xenoliths show a distinct discontinuity with those from Type I mantle xenoliths, whereas they show a continuous or overlapping relation with those from gabbroic xenoliths and the host basalts. Our petrographic and geochemical results suggest that the studied type II xenoliths appear to be cumulates derived from the host magma-related system, being formed by early fractional crystallization, although these xenoliths may not be directly linked to the host basalt.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.117-128
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• 2017

Occurrence characteristics and existing forms of U-Th containing minerals in KURT (KAERI Underground Research Tunnel) granite are investigated to understand long-term behavior of radionuclides in granite considered as a candidate rock for the geological disposal of high-level radioactive waste. KURT granite primarily consists of quartz, feldspar and mica. zircon, REE(Rare Earth Element)-containing monazite and bastnaesite are also identified. Besides, secondary minerals such as sericite, microcline and chlorite including quartz vein and calcite vein are observed. These minerals are presumed to be accompanied by a post-hydrothermal process. U-Th containing minerals are mainly observed at the boundaries of quartz, feldspar and mica, mostly less than $30{\mu}m$ in size. Quantitative analysis results using EPMA (Electron Probe Micro-Analyzer) show that 74.2 ~ 96.5% of the U-Th containing minerals consist of $UO_2$ (3.39 ~ 33.19 wt.%), $ThO_2$ (41.61 ~ 50.24 wt.%) and $SiO_2$ (15.43 ~ 18.60 wt.%). Chemical structure of the minerals calculated using EPMA quantitative analysis shows that the U-Th minerals are silicate minerals determined as thorite and uranothorite. The U-Th containing silicate minerals are formed by a magmatic and hydrothermal process. Therefore, KURT granite formed by a magmatic differentiation is accompanied by an alteration and replacement owing to a hydrothermal process. U-Th containing silicate minerals in KURT granite are estimated to be recrystallized by geochemical factors and parameters such as temperature, pressure and pH owing to the hydrothermal process. By repeated dissolution/precipitation during the recrystallization process, U-Th containing silicate minerals such as thorite and uranothorite are formed according to the variation in the concentrated amount of U and Th.