• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.1000-1007
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• 2001

In an evacuated tube solar collector, the stable sealing of the heat pipe to the glass tube is important for the collector to use for a long period of time. The sealing of copper tube to the glass is quite difficult because of the large differences in the physical and chemical properties of the two materials. In this study, therefore, a proper copper oxide layer was induced to improve the chemical bonding of the two materials, and the oxidation state of copper and the interface between copper and glass were examined by XRD, SEM and EDS. Its bonding strength was also measured. Cu$_2$O was formed when the bare copper was heat-treated under 600$^{\circ}C$, while CuO oxide layer was formed above that temperature. The bonding state of CuO to the copper was very poor. The borate treatment of the copper, however, extend the stable forming of Cu$_2$O layer to 800$^{\circ}C$. Borosilicate glass tube was sealed to a copper tube by Housekeeper method only when the sealing part was covered with Cu$_2$O layer. The bonding strength at the interface was measured 354.4N, its thermal shock resistance was acceptable.

• BMB Reports
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• v.29 no.6
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• pp.500-506
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• 1996

We have isolated a water-extracted novel regulator for blood coagulation from an earthworm, Lumbricus rubellus. As a folk remedy, the earthworm has been known to facilitate blood circulation. After complete heat inactivation of endogenous proteases in the earthworm, an anticoagulant(s) was purified through ammonium sulfate fractionation and three consecutive gel permeation chromatography of Sephacryl S-300, Sephadex G-75, and G-150 by measuring activated partial thromboplastin time (APTT) The anticoagulant was further purified to 2,800 fold with a C4 reversed-phase HPLC This activity was stable under heat ($100^{\circ}C$ for 30 min) and acidic conditions (0.4 N HCl). The effects of this partially purified anticoagulant on thrombin were observed with various substrates such as N${\alpha}$-benzoyl-DL-arginine-p-nitroanilide (BApNA), H-D-phenylalanyl-L-pipecoyl-L-arginine-p-nitroanilide (S-2238), N${\alpha}$-p-tosyl-L-arginine methyl ester (TAME), and fibrinogen as a natural substrate. Only TAME hydrolysis, due to an esterase activity of the enzyme, was inhibited among the chromogenic substrates. In addition, the anticoagulant not only inhibited the conversion of fibrinogen to fibrin but also prolonged the fibrin clot formation monitored with the in vitro coagulation test. Based on these observations, we suggest the significance of measuring the ability of antithrombotic drugs to inhibit the esterase activity of thrombin. In this report, it was also shown that the earthworm indeed contained a water-extractable, heat- and acid-stable anticoagulant which could be used as a novel antithrombotic agent.

• Korean journal of food and cookery science
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• v.32 no.3
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• pp.316-324
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• 2016

Purpose: This study chose Vaccinium oldhamii as a material to complement the redness of Sansuyu, which is unstable to heat, to Sansuyu pudding. Methods: The level of browning and hunter color of Corni fructus juice supernatant (CFS) and Vaccinium oldhamii extract (VOE) were examined and dependent on heating time and storage period. Results: A value (redness) of VOE was high, browning was moderate during the storage period, and though the storage period was extended, the value stayed stable, meaning overall redness was maintained. With the increase in the amount of added VOD, the color preference of Sansuyu pudding, and D (VOE 10.0%) was marked the highest at 5.80. As for the preference of texture, B (VOE not added) was the highest at 5.35, but C (VOE 5.0%) was marked the highest at 5.10 for overall preference. The DPPH radical scavenging ability of Sansuyu pudding was 15.86-21.39% at a concentration of 1,000 ppm, and the total polyphenol content was 136.76-139.62 mg/100 g. Since the redness of Sansuyu is unstable to heat and then is heated, its degree of browning and b value (degree of yellowness) increases. Conclusion: So if a material with a red color that is stable to heat is added to Sansuyu, the preference of Sansuyu products will improve.

• Textile Coloration and Finishing
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• v.19 no.3
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• pp.18-25
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• 2007

The fixing behaviors of anthraquinone disperse dyes containing dimethylamino substituent, such as C. I. Disperse Violet 26(D.V.26) and C. I. Disperse Blue 14(D.V.14), or containing diamino substituent, such as C. I. Disperse Blue 73(D.B.73), and monochlorotriazinyl azo reactive dyes, such as C. I. Reactive Orange 13(R.O.13), C. I. Reactive Red 3(R.R.3). C. I. Reactive Yellow 2(R.Y.2) on polyester/cotton blend(P/C) fabrics were examined for the one-step printing of P/C fabrics. The high temperature steaming of $175^{\circ}C$ is the most satisfactory fixing method for P/C one-step printing with above disperse and reactive dyes among the four different fixing methods: $175^{\circ}C$ steaming, $102^{\circ}C$ steaming${\rightarrow}175^{\circ}C$ steaming, $190^{\circ}C$ thermosol, $102^{\circ}C$ steaming${\rightarrow}190^{\circ}C$ thermosol. $190^{\circ}C$ thermosol is unfit to fix R.R.3 and R.Y.2 whose heat stability is poor. It was found that D.V.26 and D.B.14 containing dimethylamino substituent are unstable for heat and alkali, but D.B.73 is stable for them to print P/C blend fabrics with R.O.13 which is also stable for heat. Therefore we found that D.B.73, R.O.13 and a pair of D.B.73 and R.O.13 were very suitable for one-step printing of P/C blend fabrics.

• Journal of Korea Foundry Society
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• v.41 no.5
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• pp.445-453
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• 2021

Computational thermodynamics for various alloy systems is well known as the CALPHAD technique. Gibbs energy model parameters for each phase are obtained from experimentally measured thermodynamic properties and are mainly used to predict areas not experimentally measured and to analyze experimental results thermodynamically. In this study, the thermodynamic modeling of the Ni-Cr-Nb-C quaternary system is conducted for a thermodynamic analysis of the phenomena by which heat-resistant cast alloys (IN-657) are destroyed in certain areas after long-term use. The stable phases in the system according to the Cr content, phase fraction depending on the temperature, and long-range ordering parameters for the Ni₂Cr phase are calculated and compared to results obtained experimentally. The calculated thermodynamic properties suitably explain the experimentally reported fracture temperature range and the results of stable phases formed in the fractured areas. Thermodynamic modeling through the CALPHD method is expected to be useful for analyzing and predicting the thermodynamic behaviors of various cast alloys.

• Journal of the Korean institute of surface engineering
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• v.56 no.6
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• pp.401-411
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• 2023

This study investigates the synthesis, characterization, and application of zinc oxide (ZnO) nanoparticles for corrosion resistance and stress corrosion cracking (SCC) mitigation in high-temperature and high-pressure environments. The ZnO nanoparticles are synthesized using plasma discharge in water, resulting in rod-shaped particles with a hexagonal crystal structure. The ZnO nanoparticles are applied to Alloy 600 tubes in simulated nuclear power plant atmospheres to evaluate their effectiveness. X-ray diffraction and X-ray photoelectron spectroscopy analysis reveals the formation of thermodynamically stable ZnCr₂O₄and ZnFe₂O₄ spinel phases with a depth of approximately 35 nm on the surface after 240 hours of treatment. Stress corrosion cracking (SCC) mitigation experiments reveal that ZnO treatment enhances thermal and mechanical stability. The ZnO-treated specimens exhibit increased maximum temperature tolerance up to 310 ℃ and higher-pressure resistance up to 60 bar compared to non-treated ZnO samples. Measurements of crack length indicate reduced crack propagation in ZnO-treated specimens. The formation of thermodynamically stable Zn spinel structures on the surface of Alloy 600 and the subsequent improvements in surface properties contribute to the enhanced durability and performance of the material in challenging high-temperature and high-pressure environments. These findings have significant implications for the development of corrosion-resistant materials and the mitigation of stress corrosion cracking in various industries.

• Korean journal of food and cookery science
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• v.32 no.3
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• pp.270-278
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• 2016

Purpose: We have investigated for the purpose of studying change of vitamins and minerals in frequently used vegetables by low moisture cooking method. Methods: Vitamin B complex, vitamin C and mineral (Mg, Ca, K, Zn, Fe) contents are analyzed in vegetables such as spinach, cabbage, bean sprouts and carrot which are heat-treated with degrees of water contents. Low moisture cooking method represents heat-treated vegetable (LM experiment group) with 25 wt.% water content for the vegetable weight while general blanching method includes heat-treated vegetable (GB experiment group) with 500-1,000 wt.% water content for the vegetable weight. Results: Retention rate of vitamin B1 (thiamin) in the LM experiment group is relatively high (87.50-95.68%) and dosen't show considerable differences from raw vegetables. On the other hand, the retention rate of vitamin $B_1$ in GB group's cabbage and spinach dramatically decreased to 19.46-25.00%. Retention rate of vitamin B2 (riboflavin) is sustained stably in LM experiment group (75.00-87.50% in bean sprouts, cabbage and spinach), represents that low moisture cooking method has relatively higher contents in vitamin $B_2$. The LM experiment group has 71.43-85.71% on retention rate of niacin while the GB group shows relatively lower niacin (57.14-64.58%), represents conflicting results from the general idea that vitamin $B_3$ is relatively stable in heat treatment and blanching. Retention rate of pantothenic acid is considerably higher in both LM and GB experiment group, indicates vitamin pantothenic acid is relatively stable in the various cooking condition such as amount of water and heat treatment. In the experiment under various water contents, vitamin C is not detected in both bean sprouts and carrots, while the contents in cabbage and spinach are 19.87 mg/100 g and 26.65 mg/100 g respectively. In the same experiment, the retention rate of Vitamin C in LM experiment group (91.65%, 92.23%) is considerably higher than GB group (58.08%, 61.61%). Retention rate of Mg, K, Fe in the LM experiment group is relatively higher than GB group. Conclusion: Resultingly, the observations suggests that minimum water quantity and minimum heat treatment processes should be established in cooking vegetables which have soluble vitamins and minerals.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1603-1612
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• 1990

An experimental study is conducted to investigate the fluid flow and heat transfer around tubes arranged in line. All measurements are performed at Reynolds number 1.58*10$^{4}$ with varing tube spacings from the small pitch ratio(L/D=1.25) to the large pitch ratio(L/D=3.0). Mean static pressures and mean temperatures of the surface of tubes and mean velocities and turbulent intensities in tube banks are measured. The flow patterns and the characteristics of heat transfer are strongly influenced by the tube spacings. Especially, in the case of very small spacings(L/D=1.25), the flow between neighboring tubes becomes very stagnant and the heat transfer decreases. In the case of each tube spacing, the characteristics of heat transfer around the 3rd, the 4th and the 5th tubes are nearly similar to one another, because the flow around tubes becomes stable at the 3rd tubes. The local heat transfer has the peak value near the reattachment point which has the peak value of pressure, but the local heat transfer for the 2nd tube of L/D=1.25 without reattaching has the peak value at .theta.=75.deg.. For each pitch ratio, the mean heat transfer increases gradually toward the downstream tubes, because the oncoming flow through neighboring tubes comes closer to the forward and rear surfaces of the tube and the turbulent intensity becomes larger in the downstream direction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.10
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• pp.387-393
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• 2016

A ground source heat pump system maintains a constant efficiency due to its stable heat source and radiant heat temperature which provide a more effective thermal performance than that of the air source heat pump system. As an eco-friendly renewable energy source, it can reduce electric power and carbon dioxide. In this study, we analyzed one year of data from a web based remote monitoring system to estimate the thermal performance of GSHP with the capacity of 3RT, which is installed in a low energy house located in Daejeon, Korea. This GSHP system is a hybrid system connected to a solar hot water system. Cold and hot water stored in a buffer tank is supplied to six ceiling cassette type fan coil units and a floor panel heating system installed in each room. The results are as follows. First, the GSHP system was operated for ten minutes intermittently in summer in order to decrease the heat load caused by super-insulation. Second, the energy consumption in winter where the system was operated throughout the entire day was 7.5 times higher than that in summer. Moreover, the annual COP of the heating and cooling system was 4.1 in summer and 4.2 in winter, showing little difference. Third, the outlet temperature of the ground heat exchanger in winter decreased from $13^{\circ}C$ in November to $9^{\circ}C$ in February, while that in summer increased from $14^{\circ}C$ to $17^{\circ}C$ showing that the temperature change in winter is greater than that in summer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.504-516
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• 1997

Recently scientists and engineers are developing a system to get waste heat of low-temperature level with advanced heat pump, which have not been used up to now. As the reason, it is necessary to examine capability of using waste heat which is raised up in the tunnel of subway out of widely distributed low-temperature waste heat in large cities. Therefore we surveyed thermal environment of the tunnel of subway in $S\check{o}my\check{o}n$, downtown of Pusan, from November 1995 to December 1996 and developed a program to predict the thermal environment of subway on the basis of experimental data and the geometries of tunnels. This paper has proved availability of waste heat of subway when the measured results obtained in subway in the winter time and the simulated results of thermal environment prediction program are compared, as well as has reported results of estimating reliability of the simulation program. As the result, the charateristics of thermal environment in the tunnel of subway in $S\check{o}my\check{o}n$ station in the winter time are to be followed; 1) temperature in the tunnel is about $10^{\circ}C$ higher than outside air temperature, 2) temperature change in the tunnel is less than that in the platform so that we may obtain stable heat source, 3) and when the measured results obtained in subway in the winter time and the simulated results of thermal environment prodiction program is compared, both results show similar tendency. Therefore, we confirm estimating reliability of the simulation program.