• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.957-966
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• 1994

The transformation of butanes and 1-butene into aromatic compounds was performed over HZSM-5 catalyst and its Ag ion-exchanged form. The yield of aromatic hydrocarbons appreciably increased by incorporating silver cations into HZSM-5. The silver cations serve as catalysts for dehydrogenation of the starting hydrocarbons. $Ag^+$ ions could be reduced to $Ag^0$ metals with resulting in the formation of acidic OH grops by hydrogen produced during the dehydrogenation of butanes and 1-butene. The reaction of 1-butene over ZSM-5 with different loading of Ag was carried out to investigate the effect of acidic properties of these catalysts.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.2
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• pp.87-93
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• 2002

A amphipod, Leptocheirus plumulosus was exposed to Ag contaminated sediments to evaluate relative importance of various uptake routes (sediment, porewater, supplementary food) for Ag bioaccumulation in sediment-dwelling marine invertebrates. Additionally, influence of AVS (acid-volatile sulfide) on the partitioning of Ag to porewater and on the Ag bioavailability was determined to evaluate the utility of AVS criteria for the management of metal contaminated sediment. The experimental sediments were spiked with 4 levels of Ag (0.1-3.3 ${\mu}$mol Ag/g) and AVS concentrations were manipulated to 40 or <0.5 ${\mu}$mol/g, then equilibrated for >2 months to allow pore water/particulate distributions similar to nature. A L. plumulosus was incubated in the contaminated sediments with overlying water for 35d. During the exposure, the amphipods was fed with supplementary food ($TetraMin^{(R)}$) with or without Ag contamination. Following exposure, tissue Ag in L. plumulosus was strongly correlated with the weak acid extractable Ag in sediments ($r^{2}$=0.87, p<0.001). The ratio of AVS to Ag-SEM (Ag extracted simulaneouls with AVS) had a strong influence on porewater Ag concentration, consistent with previous studies. However, Ag bioaccumulation in L. plumulosus was not influenced by AVS concentrations. The amphipods fed Ag contaminated food took up ${\sim}$ 1.8 X Ag accumulated by the amphipods fed uncontaminated supplementary diet. The result suggests that the benthic invertebrates exposed to metal contaminated sediments would accumulate metals largely via ingestion of contaminated sediments and food, with minor contribution from dissolved sources of porewater and overlying water.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.169-171
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• 2006

Solderability and reaction properties were investigated for four Pb-free alloys as a function of Ag contents; Sn-4.0Ag-0.5Cu, Sn-3.0Ag-0.5Cu, Sn-2.5Ag-0.5Cu, and Sn-1.0Ag-0.5Cu. The alloy of the lowest Ag content, i.e., Sn-1.0Ag-0.5Cu, showed poor wetting properties as the reaction temperature decreased to 230oC. Variation of Ag concentration in the Sn-xAg-0.5Cu alloy shifted exothermic peaks indicating the undercooling temperature in DSC curve. For the aging process at 170oC, the thickness of IMCs at the board-side solder/Cu interface increased with the Ag concentration.

• Korean Journal of Materials Research
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• v.13 no.1
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• pp.18-23
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• 2003

Properties of Ag thick films fabricated by using low temperature curable silver pastes were investigated. Ag pastes were consisted of polymer resins and silver powders. Ag pastes were used for conductive or fixing materials between board and various electrical and electronic devices. Low temperature curable Ag pastes have some advantages over high temperature curable types. In cases of chip mounting, soldering properties were required for screen printed Ag thick films. In this study, four types of Ag pastes were fabricated with different compositions. Screen printed Ag thick films on alumina substrates were fabricated at various curing temperatures and times. Thickness, resistivity, adhesive strength and solderability of fabricated Ag thick films were characterized. Finally, Ag thick films produced using Ag pastes, sample A and B, cured at $150^{\circ}C$ for longer than 6 h and $180^{\circ}C$ for longer than 2 h, and $150^{\circ}C$ for longer than 1 h and $180^{\circ}C$ for 1 h, respectively, showed low resistivities of $10^{-4}$ $∼10^{-5}$ Ωcm and good adhesive strength of 1∼5 Mpa. Soldering properties of those Ag thick films with curing temperatures at solder of 62Sn/36Pb/3Ag were also investigated.

• Journal of Preventive Medicine and Public Health
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• v.17 no.1
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• pp.203-210
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• 1984

Primary screening test for serum HBsAg by RPHA from 4,805 persons who were clinically well through preemployment examination for the period of one calendar year of 1983 revealed 476 (9.9%) positive individual carriers. There were no significant differences in distribution of positives of serum HBsAg by age group, profession, or province area. Among positives of serum HBsAg, 356 (74.8%) showed normal findings and 120 (25.2%) showed abnormal findings in liver function test, respectively. Radioimmunoassay was done in 169 positives of HBsAg and RIA detected 10 negative persons who were positive by RPHA revealing 5.9% of false positive rate and 94.1% of sensitivity of RPHA. In RIA profile of HBV markers, pattern I (HBsAg+, Anti-HBe+) was 46.6%, pattern II (HBsAg+, HBeAg+) was 33.3%, pattern III (HBsAg+only) was 18.3%, pattern IV (HBsAg+, HBeAg+, Anti-HBs+) was 1.3%, pattern V (HBsAg+, HBeAg+, Anti-HBe+) was 0.6%, respectively. There were no positives of HBsAg among 10 persons who were negatives of HBsAg by RIA.

• Proceedings of the KIEE Conference
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• 1999.11a
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• pp.10-12
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• 1999

Optical properties of $Zn_2AgGaSe_4$ and $Zn_2AgGaSe_4$:$Co^{2+}$ crystals are investigated in the visible and near-infrared regions at 298K. The direct band gap at 298K is 1.630eV for the $Zn_2AgGaSe_4$ and 1.567eV for the $Zn_2AgGaSe_4$:$Co^{2+}$ crystals, respectively. In the optical absorption and PAS spectrum of the $Zn_2AgGaSe_4$:$Co^{2+}$, we observed five impurity absorption peaks at $4220cm^{-1}$, $5952cm^{-1}$, $12422cm^{-1}$, $12987cm^{-1}$ and $14184cm^{-1}$. These impurity absorption peaks are attributed to the electronic transitions between the split energy levels of $Co^{2+}$ ions with Td symmetry of $Zn_2AgGaSe_4$ host lattice. The crystal field parameter Dq, the Racah parameter B and the spin-orbit coupling parameter $\lambda$ are given by $442cm^{-1}$, $425cm^{-1}$ and $440cm^{-1}$, respectively.

• Journal of Preventive Medicine and Public Health
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• v.17 no.1
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• pp.47-55
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• 1984

To study the risk factors associated with maternal HBsAg carrier and the effects of maternal HBs antigenemia on the neonatal health, sera of 729 pergnant women admitted to the Keimyung University Hospital for delivery during the period of February 1-May 30. 1982 were tested for HBsAg by RPHA method and for anti-HBs by PHA method. Among them 43 women (5.9%) had HBsAg and 246 women (33.7%) had anti-HBs giving an infection rate of 39.6%. The interview data for 43 HBsAg positive mothers and randomly selected 210 HBsAg negative mothers showed a statistically significant association between acupuncture history and HBsAg positive rate (p<0.005) which suggest that acupuncture might have contributed significantly to the propagation of viral hepatitis in Korea. The living standard of HBsAg positive mothers was generally lower than that of HBsAg negative mothers which supports the hypothesis that environmental factors are associated with viral hepatitis B infection. None of the 43 neonates born to HBsAg positive mothers had HBsAg in their cord blood. Three months after birth, 35 out of 43 infants were retested and only one infant became HBsAg positive. At six months of age, 32 out of 35 infants were retested and none of them were HBsAg positive except the same infant who was positive at three months. Among 20 control infants of HBsAg negative mothers, all of them were HBsAg negative at three and six months follow-up. These findings are not consistent with the supposition that perinatal infection is a main route of viral hepatitis B transmission in south-east Asia including Korea. HBsAg positive mothers had significantly higher rate of premature delivery (27.9%) than HBsAg negative mothers (11.7%) (p<0.05). Also, the low birthweight incidence rate was higher among HBsAg positive mothers (23.3%) than negative mothers (14.1%) but this was not statistically significant (P=0.16). The premature rupture of membrane was more frequent among HBsAg positive mothers (25.5%) than negative mothers (11.1%) (p<0.05). There were no significant differences in the stillbirth rate and incidence of congenital anomalies between HBsAg positive and negative groups. It was not clarified in this study due to small sample size whether higher incidence of premature delivery and premature rupture of membranes among HBsAg positive mothers was due to HBs antigenemia per so or their lower living standard than HBsAg negative mothers.

• Journal of the Korean Magnetics Society
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• v.11 no.2
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• pp.63-71
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• 2001

The effects of an Ag seed layer on the magnetic properties and the microstructural evolution of SmCo/Cr thin films deposited on glass substrates were investigated. Coercivity of the films is 2.0 kOe when the thickness of Ag seed layer was 1nm thick, but it increased to 2.7 kOe when the Ag seed layer thickness is 3 nm. The increase of coercivity for film with 3 nm-thick Ag is due to roughness of Cr and grain size of Cr by the Ag microbumps. Ar partial pressure influenced on the formation of Ag microbumps, for example, they were formed at 5 mTorr when Ag thickness was 1 nm. The mechanism of magnetization reversal of the SmCo films changed from domain wall motion to domain rotation as the Ag inserted. This was thought to be due to inhibition of domain wall motion by the reduction of Cr grain size and the increase of roughness.

• Journal of Preventive Medicine and Public Health
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• v.22 no.1 s.25
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• pp.65-70
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• 1989

To examine the association between serum HBeAg status and tuberculosis infection, we reviewed medical records of 579 inpatients who had serum HBeAg test with RIA method at the Department of Nuclear Medicine of Kyungpook University Hospital from January 1, 1985 to December 31, 1987. HBeAg positive patients had lower tuberculosis infection rate(5.0%) than that of HBeAg negative patients(9.8%) and the odds ratio of HBeAg associated with tuberculosis was 0.48(95% C.I.:0.22-1.08). Similar relationship was found in the patients of hepatobiliary diseases; tuberculosis infection rate was 4.4% in HBeAg positive patients, 8.1% in HBeAg negative patients, and the odds ratio was 0.52(95% C.I.:0.17-1.35). Although the association did not reach the statistical significance level of 0.05, the negative association was consistent with other study done on Southeast Asian population of Philadelphia. A cohort study in general population is warranted to confirm above findings because of the limitations on hopital-based data.

• Bulletin of the Korean Chemical Society
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• v.6 no.4
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• pp.202-206
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• 1985

The crystal structure of The crystal structure of $Ag^+$-Exchanged Zeolite A, $Ag_{4.6}Na_{7.4}-A$, dehydrated, treated with $H_2$, and evacuated, all at $350^{\circ}C$, has been determined by single crystal x-ray diffraction methods in the cubic space group Pm3m at $24(1)^{\circ}C;$ a = $12.208(2)\AA.$ The structure was refined to the final error indices R1 = 0.088 and R2 (weighted) = 0.069 using 194 independent reflections for which II_0$ > $3{\sigma}(I_0)$. On threefold axes near the centers of 6-oxygen rings, $7.4 Na^+$ ions and $0.6 Ag^+$ ions are found. Two non-equivalent 8-ring $Ag^+$ ions are found off the 8-ring planes, each containing about $0.6 Ag^+$ ions. Three non-equivalent Ag atom positions are found in the large cavity, each containing about 0.6 Ag atoms. This crystallographic analysis may be interpreted to indicate that $0.6 (Ag_6)^{3+}$ clusters are present in each large cavity. This cluster may be viewed as a nearly linear trisilver molecule $(Ag_3)^0$ (bond lengths, 2.92 and 2.94 $\AA;$ angle, $153^{\circ})$ stabilized by the coordination of each atom to a Ag^+$ ion at 3.30, 3.33, and 3.43 $\AA$, respectively. In addition, one of the silver atoms approaches all of the 0(1) oxygens of a 4-ring at $2.76\AA.$ Altogether $7.4 Na^+$ ions, $1.8 Ag^+$ ions, and 1.8 Ag atoms are located per unit cell. The remaining $1.0 Ag^+$ ion has been reduced and has migrated out of the zeolite framework to form silver crystallites on the surface of the zeolite single crystal.