• Korean Journal of Metals and Materials
• /
• v.46 no.11
• /
• pp.737-746
• /
• 2008

Mechanisms of sticking phenomena occurring during hot rolling of a modified STS 430J1L ferritic stainless steel have been investigated in this study by using a pilot-plant-scale rolling machine. As the rolling pass proceeds, the Fe-Cr oxide layer formed in a reheating furnace is destroyed, and the destroyed oxides penetrate into the rolled steel to form a thin oxide layer on the surface region. The sticking does not occur on the surface region containing oxides, whereas it occurs on the surface region without oxides by the separation of the rolled steel at high temperatures. This indicates that the resistance to sticking increases by the increase in the surface hardness when a considerable amount of oxides are formed on the surface region, and that the sticking can be evaluated by the volume fraction and distribution of oxides formed on the surface region. The lubrication and the increase of the rolling speed and rolling temperature beneficially affect to the resistance to sticking because they accelerate the formation of oxides on the steel surface region. In order to prevent or minimize the sticking, thus, it is suggested to increase the thickness of the oxide layer formed in the reheating furnace and to homogeneously distribute oxides along the surface region by controlling the hot-rolling process.

• Korean Journal of Metals and Materials
• /
• v.50 no.12
• /
• pp.921-929
• /
• 2012

The pulsed current activated sintering method (PCAS) is a new rapid sintering method that was developed recently for fabricating ceramics and composites. This method combines a high temperature for a short time with pressure application. In this work, PCAS was used to fabricate $WC-5wt%Mo_2C-5wt%$ Co hard material using WC, $Mo_2C$, and Co. The $WC-Mo_2C-Co$ was almost completely dense with a relative density of up to 100% after the simultaneous application of a pressure of 60 MPa and electric current for 11 min without grain growth. The average grain size of WC that was produced through PCAS was about $0.5-0.6{\mu}m$. The vickers hardness and fracture toughness of the $WC-5wt%Mo_2C-5wt%$Co hard materials were about $2453.5kg/mm^2$ and $7.9MPa{\cdot}m^{1/2}$, respectively, for 60 MPa at $11200^{\circ}C$.

• Composites Research
• /
• v.22 no.2
• /
• pp.1-6
• /
• 2009

The mechanical characteristics of gamma-ray irradiated UHMWPE specimens were investigated under various heat treatment conditions. The heat treatment was performed in the range of annealing and remelting temperatures. The annealing treatment below the temperature of $130^{\circ}C$ hardly induced changes in the tensile strength, the strain at the failure and the hardness. However the remelting treatment above $140^{\circ}C$ deteriorated those mechanical properties. It was shown in an FTIR analysis that the annealing treatment caused some oxidation of free radicals created by the pretreatment of the irradiation. These quantitative data represented by the behavior of mechanical properties might be used as basic informations for the design and analysis of various artificial joints.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.4 no.3
• /
• pp.223-229
• /
• 1994

$KTP(KTiOPO_4)$ single crystals have been hydrothermally grown in KOH solutions. Properties and Raman spectra of grown crystal were investigated. The most effective solvents for the crystal growth of KTP were KOH and KF solutions. In this study, the properties of KTP single crystals grown hydrothermally at $500^{\circ}C$ in 9 m KOH solution were measured. The following results were obtained : lattice parameters ; a=1.281 nm and c=1.058 nm, density ; $2.94 g/cm^3$, Vickers hardness ; $562kg/cm^2$, refractive indices ; $n_e=1.740$ and $n_e= 1.747.$ And Raman spectra of hydrothermal growth KTP single crystal have been investigated at room temperature under atmospheric pressure. As a result, the $A_1$ modes agree very well with KTP single crystal of high temperatures solution growth but the behavior of $B_2$ modes were slightly different.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.43 no.9
• /
• pp.1423-1430
• /
• 2014

This study investigated the effects of superheated steam (SHS) and high hydrostatic pressure (HHP) on the quality of Galbijjim. SHS cooking increased moisture and crude fat contents and decreased crude protein contents (P<0.05). The value of L was significantly higher upon SHS cooking compared to conventional cooking (CC), whereas a and b values were not significantly different among the samples. Hardness decreased more upon CC than SHS. The results of the safety storage experiment at refrigeration temperature showed that the total number of bacteria was lower in SHS-HHP than in CC-HHP. The thiobarbituric acid value increased to 0.70~1.56 mg malonaldehyde (MA)/kg in CC-HHP after 15 days, and SHS-HHP showed 0.69 (0 day)~1.24 (15 days, $10^{\circ}C$) mg MA/kg. Volatile basic nitrogen value was 18.07~36.76 mg% in CC-HHP, and that in SHS-HHP also increased to 17.06 (0 day)~35.76 mg% (15 days, $10^{\circ}C$). Overall, SHS cooking and HHP reduced microorganisms, which could improve product quality and sanitation.

• Restorative Dentistry and Endodontics
• /
• v.8 no.1
• /
• pp.89-96
• /
• 1982

The purpose of this study is to identify the phases of four different types, low-copper lathe cut (Type II, class 1) and spherical (Type II, class 2) amalgam alloys which are made by Caulk company and high copper Dispersalloy (Type II, class 3) made by Johnson & Johnson and Tytin (Type I, class 2) made by S.S. White and to determine the Vickers hardness number on the individual phase and four different types of dental amalgam. After each amalgam alloy and Hg measured exactly by the balance was triturated by the mechanical amalgamator (De Trey), the triturated mass was inserted into the cylindrical metal mold which was 4 mm in diameter and 12mm in height and was pressed by the Instron Universal Testing machine (Model 1125) at the speed of 1mm/minute with 143$kg/cm^2$ according to the A.D.A. Specification No. 1. The Specimen removed from the mold, mounted and stored in the room temperature for 7 days. The speciman was polished with the emery paper from #220 to #1200 and finally on the polishing cloth with 0.3 and 0.05 um $Al_2O_3$ powder suspended in water. And then each specimen was etched by Allan's method and washed with Sodium Bisulfinite for 30 seconds. Finally differentiation and metallography on each phase were obtained by using metallographical microscope (Versamet, Union) and microhardness was obtained by using microhardness tester (MVH-2, Torsee). The results were as follows: 1. In the low-copper amalgam, the ${\gamma}$, ${\gamma}_1$ and ${\gamma}_2$ phase were observed and in the high-copper amalgam, the ${\gamma}$, ${\gamma}_1$. ${\epsilon}$ and ${\eta}$ phases were observed but ${\gamma}_2$ phase was not observed. 2. Among the microhardness of each amalgam phase measured under pressing a vickers diamond indenter with 2.0gm load for 30 seconds, e phase has the highest V.H.N (314 ${\pm}$ 20), and in low-copper amalgam 12 phase has the lowest V.H.N. (29${\pm}$1) and ${\eta}$ phase which was observed in high-copper amalgam has 230${\pm}$13 V.H.N and this phase is considerd to contribute to strengthen the handness in amalgam. 3. The V.H.N. measured under pressing a Vickers diamond indenter with 300.0gm load for 30 seconds in low-copper amalgam was lower than that of high-copper amalgam.

• Korean journal of food and cookery science
• /
• v.11 no.2
• /
• pp.126-132
• /
• 1995

This study was undertaken to determine effect of parboiling on physical and cooking characteristic properties of milled rice. Equilibrium moisture content(EMC) of parboiled rice soaked at room tempe-rature(25$^{\circ}C$) and high temperature(75$^{\circ}C$) increased 1.8∼2.7 times & 1.4∼l.6 times as compare to raw rice, and time to reach EMC of parboiled rice became longer 4 times and 1.7 times than raw rice respectively. Equilibrium volume(EV), time to reach EV and volume increase rate constants(ku) were similar to EMC, time to reach EMC, and k. kv of parboiled rice brought about in decrease at room temperature and increase at high temperature. The geletinization temperature, time and peak viscosity of parboiled rice were higher than those of raw rice. Parboiling brought about in decrease in L/W of cooked parboiled rice kernels and L/W increased according to presoaking time was prolo-nged. Solid content of cooking water of raw rice were higher than those of parboiled rice. Hardness of uncooked PL20 & PL40 soaked for 30 min was higher than that of raw rice but that of uncookef parboiled rice soaked for 90 min was lower than that of raw rice. Springness of cooked parboile rice for initial 10 min decresed with that of cooked raw rice and then increased sharply, cooked f, r 15 min then increased slowly, cooked parboiled rice for 40 min increased more than cooked raw rice. Color differences($\Delta$I) of PT2O samples was the lowest L value of all the samples increased but a and b value decreased according to milling degree was high.

• Korean Journal of Food Science and Technology
• /
• v.27 no.6
• /
• pp.1017-1027
• /
• 1995

This study was attempted to investigate physicochemical properties, molecular structural properties of native and acid-treated chestnut starch and chestnut starch gel. The amylose content was 18.9% and X-ray diffraction pattern showed Cb type. Swelling power was increased abruptly in the range of $65^{\circ}C{\sim}75^{\circ}C$ but increased slowly after that and solubility was increased abruptly until $70^{\circ}C$ but increased slowly after that. In amylograms which have different heating temperatures, cooling viscosity at $50^{\circ}C$ was reduced as heating temperature was increased. In molecular structural properties of amylose, ${\lambda}_{max}$ was 640 nm, ${\beta}-amylolysis$ limit was 84.2% and the degree of polymerization was 951 and in those of amylopectin, ${\lambda}_{max}$ was 570 nm, ${\beta}-amylolysis$ limit was 58.2%, the degree of polymerization was 1371 and average chain length was 22.6. In gel chromatography elution profiles of starch and amylose, 4.0% and 11.5% of low molecular weight-molecules($<5{\times}10^5$) were leached out. In gel chromatography elution profiles of soluble starch, the higher heating temperature was, the more high molecular weight-starches were leached out. The elution profiles after debranching amylopectin with pullulanase showed 2.2 of the ratio of peakIII(DP 10-15) to peakII(DP 35-45). Acid hydrolysis extent of 2.2 N HCI-treated starch at $35^{\circ}C$ for 10 days was 96% and hydrolysis rate showed two step pattern which had border line at 4 days. In elution profiles of acid treated chestnut starch, amylopectin peak was disappeared compeletly after 6 hrs and converted short chains of DP 10-15. Amylose content was increased until 6 hrs but decreased after that. Hardness of starch gel made at $75^{\circ}C$ of heating temperature and cohesiveness of starch gel made at $85^{\circ}C$ of heating temperature were the highest. Retrogradation rate of starch gels were relatively high, especially for the starch gel made at $75^{\circ}C$ of heating temperature.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.40 no.7
• /
• pp.1017-1024
• /
• 2011

Korean wheat semolina (FS: fine semolina) with similar characteristics to durum wheat semolina was substituted at rates of 0, 10, 20, 30, 40, and 50% in pasta dough and the physical and cooking characteristics were investigated for making optimal pasta. Water absorption of the dough increased with the 10, 20, and 30% substitution ratio of FS. Development times were high with >30% substituted FS. This result positively influenced an increase in production and the preparation of the fresh noodle pasta. Furthermore, soft textured fresh noodles could be made due to the decrease in stability and increased weakness of the >30% substituted FS. The amylograph gelatinization characteristics of Korean wheat semolina exhibited an increase of gelatinization temperature and decrease of maximum viscosity when compared with durum wheat. The handling property of the dough showed more than 4 points in all sample groups. Weight and volume decreased and turbidity and cooking loss increased according to the increasing amount of substituted FS. However, samples with ${\leq}$ 30% FS substitution ratio had similar volumes and cooking losses when compared to the control. The L- and a-values increased and the b-value of color decreased as more FS was added. In a texture analysis, the hardness of the cooking noodles showed a low value with the >30% substituted FS. Springiness, gumminess, and chewiness exhibited a high value. In the results of a sensory evaluation, overall acceptability was high score with more than 7 points for the 30% added FS. The preferences for pasta colors were divided into white, which is similar to the Korean traditional noodle, and yellow, which is similar to durum wheat. Flavor and taste were not affected by substituting with FS. Low hardness and high chewiness was the most preferred noodle. These results suggest that >30% substituted FS was suitable for increasing quality and organoleptic qualities of Korean wheat pasta.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.39 no.1
• /
• pp.27-37
• /
• 1994

To catch the relative importance of varietal and environmental variation in various grain quality components associated with palatability of cooked rice, grain appearance, milling recovery, several physicochemical properties of milled rice and texture or eating quality of cooked rice for rice materials of five japonica cultivars, produced at four locations of the mid-mountainous and alpine area of Korea in 1989, were evaluated and analyzed the obtained data. Highly significant varietal and locational variations were detected in 1000-grain weight, amylose content, K/Mg ratio, gelatinization temperature, peak viscosity, breakdown and setback viscosities as compared with variety x location interaction variation. Also, marked locational variations were recongnized in milling recovery from rough to brwon rice, alkali digestibility and protein content, and significant varietal variation was caught in stickiness /hardness ratio of cooked rice. The variety x location interaction variation was especially large in quality components of grain appearance and ripening, palatability of cooked rice and consistency viscosity. One thousand kernel weight was heaviest in Jinbuolbyeo and Odaebyeo, and the unfilled grain ratio was lowest in Jinbuolbyeo. Odaebyeo showed slightly' lower ratio of intact and clear milled rice because of more chalky rice kernels compared with other cultivars. Amylose content of Jinbuolbyeo and Sobaegbyeo was about 1% lower than that of others and K/Mg ratio of Odaebyeo was the lowest one among rice materials. Odaebyeo, Sobaegbyeo and Jinbuolbyeo revealed significantly low gelatinization temperature and setback viscosity while high peak and breakdown viscosities. Cholwon rice showed the greatest kernel weight, good grain filling but lowest ratio of intact and clear milled rice while Jinbu rices exhibited the highest milling recovery from rough to brown rice and ratio of sound milled rice. Amylose content of milled rice in Jinbu rices was about 2-3% lower than those in other locations. Protein content of polished rice was about 1% lower in rice materials of middle zone than those of southern part of Korea. K/Mg ratio of milled rice was highest in Jinbu rice and potassium content was slightly higher in the rice materials of middle region than in those of southern region. Alkali digestion value and gelatinization temperature of polished rice was markedly high in Jinbu rices as compared with other locations. Breakdown viscosity was hightest in Chlown rices and next higher with the order of Hwaso>Unbong>Jinbu rices, and setback viscosity was the quite contrary tendency with breakdown. The stickiness /hardness ratio of cooked rice was relatively higher value in Cholwon rices than in the others and the palatability of cooked rice was a little better in Unbong and Cholwon rices than in Jinbu and Hwaso rices, although variety x location interaction variation was large. The rice materials can be classified largely into two groups of Jinbu and the others by the distribution on the plane of 1st and 2nd principal components (about 60% of total informations) contracted from twelve grain quality properties closely associated with eating quality of cooked rice. Also, Jinbu and the other rices were divided into two and three rice groups respectively. Varietal variation of overall rice quality was smallest in Hwaso. The most superior rice group in overall quality evaluation included Odaebyeo produced at Cholwon, Unbong and Hwaso, and Sobaegbyeo grown at Unbong