• Journal of Ginseng Research
• /
• v.20 no.1
• /
• pp.54-59
• /
• 1996

Red Ginseng extracts sol'n was sterilized at 85f for 20 mins and/or stored at 4$0^{\circ}C$ for 6 months and centrifuged for 20 mins at 8,500xg in order to investigate the changes in chemical components of supernatants and the properties of precipitates. Contents of crude saponin and ginsenoside-$Rb_1$, -$Rg_1$, -Re were partially decreased during heating and storage. Starch contents were decreased from 26.81% in red ginseng extracts to 17.50-8.81% in supernatants, whereas free sugar contents were increased from 15.50% to 20.29~21.35% by heating and storage. The contents of protein and minerals in supernatants were decreased, but acidic polysaccharides and polyphenol compounds were not changed. pH values of supernatants and precipitates were decreased. The absorbances of brown color precursor and brown pigment in precipitates, detected at 285 nm and 440 nm were remarkably increased. The Overa11 data suggest that precipitates in red ginseng extracts sol'n formed during steilization and storage are provably the brown pigments resulting from Maillard reaction of amino compounds with reducing sugar which could be released from starch and protein matrix and $Cu^+$, $Ca^{2+}$ and $Fe^{3+}$ ions are implicated with the reaction incorporated.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.9 s.180
• /
• pp.2319-2325
• /
• 2000

This thesis studied that seven kinds of residual elements(inclusions) had influenced on fracture toughness($K_{IC}$) obtained by Begley-Logsdon and Rolfe-Novak model equation using tensile an d impact test data of I%CrMoV HP(high pressure) rotor steel. $K_{IC}$ design curve of ASME and fracture surface by SEM were also considered, obtained results are summarized as follows $K_{IC}$ was linearly increased with increase of temperature, effect of the inclusions was significantly over FATT. $K_{IC}$ at lower shelf temperature was quantitatively related to yield strength and was agreed well with Begley's equation. It was difficult to determine $K_{IC}$ because of specimen size and tester capacity at upper shelf temperature, but for this view point Rolfe-Novak's equation was useful. The degree of brittle fracture was dependent on FATT fundamentally, adding S, Sb to matrix decreased impact energy and adding Cu, As increased yield(tensile) strength, and the influence of the others minority inclusion was comparatively insignificant.

• Journal of Microbiology
• /
• v.34 no.2
• /
• pp.198-205
• /
• 1996

Two proteases were partially characterized from culture filtrate of Mycobacterium, tuberculosis KIT110. Their molecular weights were approximately 200 and 180 kDa, respectively and they exhibited similar enzymatic characteristics. These enzymes were inhibited significantly by EDTA and to some extent by EGTA. Their activity was enhanced by $Ca^{2+}$ and $Mg^{2+}$ to some degree. However, $Cu^{2+}$ and $Ag^{2+}$ completely inhibited the enzyme activity at the concentration of 2.5 and 5 mM, respectively. The optimal pH was 7.0 and optimal temperature was around $40^{\circ}C$. These enzymes were rapidly inactivated at $80^{\circ}C$. Therefore, they were heat-labile, neutral metalloproteases. These enzymes exhibited antigenicity shown by their reacting with sera from the partients with pulmonary tuberculosis. These enzymes were able to degrade serum proteins including hemoglobin, bovine serum albumin, lysozyme and immunoglobulin G and structural matrix protein such as type I collagen. Therefore, these enzymes may be thought to contribute to tissue necrosis and pathogenesis during infection.

• Journal of Conservation Science
• /
• v.1 no.1 s.1
• /
• pp.60-79
• /
• 1992

In relation to the scientific conservation treatment of ancient gilt bronze, the gold film coated on the bronze excavated from Hwangnam Great Tomb of Old Silla Kingdom(A. D. 5C) was studied in the view of coating technology and metallurgy of bronze. The uniform and dense gold film containing $2.44\sim12.40%$ of Hg with the thickness of $5.99\sim12.97{\mu}m$ was found to be coated on the bronze objects by amalgam coating method. On silver objects, the film with the thickness of $19.96{\mu}m$ was coated also continously and uniformly with gold by the same method. The bronze objects was fabricated by forging technique and contained almost $4.7\sim11.5%$ of Pb. Its microstructure was $\alpha-phase$ solid solution including Pb segregation in the matrix. The amount of $0.4\sim2.0%$ Zn was added in the bronze for the purpose of easy fabricating of Cu alloy. Based on the data studied, the gold film on bronze sample was reproduced by amalgam coating method and compared with the ancient gold film.

• Journal of Korea Foundry Society
• /
• v.12 no.6
• /
• pp.442-449
• /
• 1992

Grey cast iron containing a small amount of Cu and Mo to improve the effect of heat treatment and microstructure were cast and them austenitized. After austenitizing the specimens of castings were austempered at 250$^{\circ}C$, 300$^{\circ}C$ and 350$^{\circ}C$. The effects of matrix structures on mechanical properties and fracture characteristics at the different austempering temperature were investigated. Tensile strength, hardness and impact toughness of austempered grey cast iron showed maximum valve 359 MPa, 321 HB, 3.9 CVN respectively at the lowest austempering temperature, 250$^{\circ}C$. $K_{IC}$ of gref cast iron at a austempering temperature, 250$^{\circ}C$, showed maximum 44 MPa.$m^{1/2}$ even though the amount of retained austenite in it is only 16%. This mainly comes from the refinement of the retained austenite. Quasi-cleavage pattern with a little fit of fibrous pattern was shown on the fractured surface of austempered grey cast iron at all of the temperatures tested.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2004.05a
• /
• pp.70-73
• /
• 2004

The packaging of the integrated circuits requires knowledge of ceramics and metals to accommodate the fabrication of modules that are used to construct subsystems and entire systems from extremely small components. Composite ceramics (Al$_2$O$_3$-SiO$_2$) were tested for substrates. A stress analysis was conducted for a linear work-hardening metal cylinder embedded in an infinite ceramic matrix. The bond between the metal and ceramic was established at high temperature and stresses developed during cooling to room temperature. The calculations showed that the stresses depend on the mismatch in thermal expansion, the elastic properties, and the yield strength and work hardening rate of the metal. Experimental measurements of the surface stresses have also been made on a Cu/Al$_2$O$_3$-SiO$_2$ceramic system, using an indentation technique. A comparison revealed that the calculated stresses were appreciably larger than the measured surface stresses, indicating an important difference between the bulk and surface residual stresses. However, it was also shown that porosity in the metal could plastically expand and permit substantial dilatational relaxation of the residual stresses. Conversely it was noted that pore clusters were capable of initiating ductile rupture, by means of a plastic instability, in the presence of appreciable tri-axiality. The role of ceramics for packaging of microelectronics will continue to be extremely challenging.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.11a
• /
• pp.308-312
• /
• 2003

The packaging of the integrated circuits requires knowledge of ceramics and metals to accommodate the fabrication of modules that are used to construct subsystems and entire systems from extremely small components. Composite ceramics ($Al_2O_3-SiO_2$) were tested for substrates. A stress analysis was conducted for a linear work-hardening metal cylinder embedded in an infinite ceramic matrix. The bond between the metal and ceramic was established at high temperature and stresses developed during cooling to room temperature. The calculations showed that the stresses depend on the mismatch in thermal expansion, the elastic properties, and the yield strength and work hardening rate of the metal. Experimental measurements of the surface stresses have also been made on a $Cu/Al_2O_3-SiO_2$ ceramic system, using an indentation technique. A comparison revealed that the calculated stresses were appreciably larger than the measured surface stresses, indicating an important difference between the bulk and surface residual stresses. However, it was also shown that porosity in the metal could plastically expand and permit substantial dilatational relaxation of the residual stresses. Conversely it was noted that pore clusters were capable of initiating ductile rupture, by means of a plastic instability, in the presence of appreciable tri-axiality. The role of ceramics for packaging of microelectronics will continue to be extremely challenging.

• Journal of Welding and Joining
• /
• v.16 no.3
• /
• pp.157-166
• /
• 1998

Recently as environmental pollution caused by Pb has posed a serious threat to the global environment, the trend to regulate the usage of Pb in electronic industry is one the rise. Currently, the solder alloy with high Pb content, Sn-37%Pb, is utilized in the electronic assembly therefore, the objective of this study is to develop an alternative solder alloy for the existing Sn-37%Pb solder alloy. First thing, this work choosed Sn-5%Pb-1.5%Ag, Sn-5%Pb-1.5%Ag-x%Bi(x=1~5%) for candidate solder alloys, and examined their properties such as melting range, wettability, microhardness, tensile property, oxidation behavior and microstructure. Wettability was on the same level of Sn-37%Pb. Dissolution of Pb ion in Sn-5%Pb solder was 0.46ppm. This solder alloy revealed cellular dendrite microstructure $\beta$-Sn matrix, Pb-rich phase, Ag/Sn, and Cu/Sn Intermetallic compounds. The range of solidification temperature was within 3$0^{\circ}C$. Also these alloy displayed higher tensile strength and lower elongation than Sn-37%Pb. The resistance of oxidation in Sn-5%Pb-1.5%Ag solder alloy was superior to that of Sn-37%Pb solder alloy. But that of Sn-5%Pb-1.5%Ag-5%Bi solder alloy was equal to that of Sn-37%Pb solder alloy.

• Korean Journal of Metals and Materials
• /
• v.49 no.9
• /
• pp.699-707
• /
• 2011

P122 steel, with a composition of Fe-10.57%Cr-1.79%W-0.96Cu-0.59Mn was arc-welded and oxidized between $600^{\circ}C$ and $800^{\circ}C$ in air for up to 6 months. The oxidation rates increased in the order of the base metal, weld metal, and heat-affected zone (HAZ), depending on the microstructure. The scale morphologies of the base metal, weld metal, and HAZ were similar because it was determined mainly by the alloy chemistry. The scale consisted primarily of a thin $Fe_2O_3$ layer at $600^{\circ}C$ and $700^{\circ}C$ and an outer $Fe_2O_3$ layer and an inner ($Fe_2O_3$, $FeCr_2O_4$)-mixed layer at $800^{\circ}C$. The microstructural changes resulting from heating between $600^{\circ}C$ and $800^{\circ}C$ coarsened the carbide precipitates, secondary Laves phases, and subgrain boundaries in the matrix, resulting in softening of the base metal, weld metal, and HAZ.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.12
• /
• pp.1108-1112
• /
• 1994

25-Acetoxy-26,27,28-trimethoxycalix[4]arene was synthesized by the treatment of calix[4]arene trimethyl ether with acetyl chloride in the presence of NaH. The solution conformation was inferred as a partial cone conformation based on the $^1H$-and $^{13}C$ NMR spectra. The crystal structure has been determined by X-ray diffraction method. The crystals are monoclinic, space group $P2_1$/n, a=8.186 (1), b=17.137 (2), c=19.878 (3) ${\AA}$, ${\beta}$=95.67 (1)$^{\circ}$, Z=4, V=2774.90 ${\AA}^3$, $D_c$= 1.22 g $cm^{-3}$, $D_m$=1.23 g $cm^{-3}$. The intensity data were collected on an Enraf-Noninus CAD-4 Diffractometer with a graphite monochromated $Cu-K{\alpha}$ radiation. The structure was solved by direct method and refined by full-matrix least-squares methods to a final R value of 0.054 for 3675 observed reflections. The molecule possesses a partial cone conformation with one flattened phenyl unit, in which one anisol ring, distal to the ester ring, is inverted. The acetoxyphenyl ring is flattened.