• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.167-174
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• 2005

Smaller size and higher integration of electronic components make smaller gap between metal conducting layers in electronic package. Under harsh environmental conditions (high temperature/humidity), electronic component respond to applied voltages by electrochemically ionization of metal and metal filament formation, which lead to short failure and this phenomenon is termed electrochemical migration(ECM). In this work, printed circuit board(PCB) is used for determination of ECM characteristics. Copper leads of PCB are soldered by eutectic solder alloys. Insulation breakdown time is measured at $85^{\circ}C,\;85{\%}RH$. CAF is the main mechanism of ECM at PCB. Pb is more susceptible to CAF rather than Sn, which corresponds well to the corrosion resistance of solder materials in aqueous environment. Polarization tests in chloride or chloride-free solutions fur pure metal and eutectic solder alloys are performed to understand ECM characteristics. Lifetime results show well defined log-normal distribution which resulted in biased voltage factor(n=2) by voltage scaling. Details on migration mechanism and lifetime statistics will be presented and discussed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.348-354
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• 2015

Urethane waterproofing materials which currently being used most commonly in the Korean domestic market have high applicability and construct layers without forming any joints, but under the influence of low temperature and low humidity, as well as the thickness of the applied layer, the curing time of this material may become extended in construction sites. To resolve these issues, a proposed method of using water-hardening type of polyurethane waterproofing materials are being developed. However, there currently lacks any standards or evaluation methods on determining an optimal mixture ratio of water for the water-hardening polyurethane waterproofing materials. Therefore, workers and construction workers are relying on their hands-on-skills and experience to determine this ratio and are not able to obtain a consistent performance quality out of these materials. Therefore, for the establishment of a board applicability of the water-hardening polyurethane waterproofing methods in construction sites, this study objectively analyzes the changes in the performance of these materials depending on the changes of the water mixture ratio and attempts to procure the optimal ratio on the basis of forming a provisionary standard. The study prepares mixtures of varying ratio(no water added, 5, 10, 15, 20, 25, 30, 40 and 50) and conducts comparative analysis respective mixtures' performances and their changes in the physical properties in an objective manner and proposes a provisional optimal value that can serve as a data base that can be used as a reference for future studies.

• Journal of Periodontal and Implant Science
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• v.28 no.2
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• pp.235-247
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• 1998

Calcium sulfate has a long history of medical use as an implant material. The biocompatibiliry of the material has been clearly established. Bone ingrowth concomitant with resorption occurs rapidly with efficient conduction of bone from particle to particle. Calcium sulfate also has a potential for functioning as a good bamer membrane. The purpose of this study was to compare the biocompatibility of different types of calcium sulfate grafting materials including an expelimental calcium sulfate compound on periodontal ligament cells in vitro as a preliminary test towards the development of a more convenient and useful form of grafting material which could promote regeneration of periodontal tissue. Human periodontal ligament cells were collected from the premolar teeth extracted for orthodontic treatment. cells were cultured in a.MEM culture medium containing 20% FBS, at $37^{\circ}C$ and 100% humidity, in a 5% CO2 incubator. Cells were cultured into 96 well culture plate $1{\times}104$ cells per well with $\alpha$-MEM and incubated for 24 hours. After discarding the medium, those cells were cultured in $\alpha$-MEM contained with 10% FBS alone (control group), in medcal-grade calcium sulfate(MGCS group), in plaster(plaster group), experimental calcium sulfate paste(CS paste group) for 1, 2, 3 day respectively. And then each group was characterized by examining of the cell counting, MTI assay, collagen synthesis. The results \vere as follows. 1. In the analysis of cell proliferation by cell counting, both medical-grdde calcium sulfate group and plaster group showed no stastically significant difference at day 1, 2, 3 accept for plaster group at day 1 compared to control group, but there was stastically significant difference between CS paste group and all other groups at day 1, 2, 3(P<0.05). 2. In the analysis of cytotoxicity by MIT assay, both medical-grade calcium sJlfate group and plaster group showed no stastically significant difference compared to control group at day 1, 2, 3 but there was stastically significant difference between CS paste group and all other groups at day 1, 2, 3(P<0.OS). 3. In the analysis of collagen synthesis by immunoblotting assay, high level was detected for medical-grade calcium sulfate group and plaster group at day 1, 2, 3 compared to CS paste group. On the basis of these results, medical-grade calcium sulfate and plaster was shown to possess biocompatibility whereas the CS paste had unfavourable outcome. This observation shows a need for modification of the materials contained in calcium sulfate paste.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.2
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• pp.203-209
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• 2008

Recrystallization characteristics of salt after removing bittern and impurities from solar salt (SD) were investigated. To remove the bittern, the SD was treated at 30, 40 and $50^{\circ}C$ under 95% humidity. 86% of the bittern was removed when the SD was kept at $30^{\circ}C$ for three weeks. Total amount of impurity in SD was 6.94% (w/w) with organic impurity (5.58%) and inorganic impurity (1.36%). Most organic impurities (89%) were soluble. When the SD was roasted at $350^{\circ}C$ for 40 minutes, 90.14% of the soluble organic impurities were removed; however, the removable organic impurity was reduced, when the SD roasted for 50 minutes at $350^{\circ}C$. L* value decreased while a* and b* values increased when the SD was roasted until 40 minutes at $350^{\circ}C$. In contrast, L* value increased while a*, b* values decreased with SD roasted over 50 minutes at $350^{\circ}C$. The size of recrystallized pure salt was positively correlated to temperature and depth of salt solution, while the crystallization time was negatively correlated to temperature and salinity. Yield of recrystallized salt was negatively correlated to temperature. Overall acceptability tended to increase at low crystallization temperature and high salinity.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.594-602
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• 2010

Since the requirement of the high density integration and thin package technique of semiconductor have been increasing, the main package type of semiconductor will be a chip scale package (CSP). The changes of diffusion coefficient and moisture content ratio of epoxy resin systems according to the change of liquid type epoxy resin and fillers for CSP applications were investigated. The epoxy resins used in this study are RE-304S, RE310S, and HP-4032D, and Kayahard MCD as hardener and 2-methylimidazole as catalyst were used in these epoxy resin systems. The micro-sized and nano-sized spherical type fused silica as filler were used in order to study the moisture absorption properties of these epoxy molding compound (EMC) according to the change of filler size. The temperature of glass transition (Tg) of these EMC was measured using Dynamic Scanning Calorimeter (DSC), and the moisture absorption properties of these EMC according to the change of time were observed at $85^{\circ}C$ and 85% relative humidity condition using a thermo-hygrostat. The diffusion coefficients in these EMC were calculated in terms of modified Crank equation based on Ficks' law. An increase of diffusion coefficient and maximum moisture absorption ratio with Tg in these systems without filler can be observed, which are attributed to the increase of free volume with Tg. In the EMC with filler, the changes of Tg and maximum moisture absorption ratio with the filler content can be hardly observed, however, the diffusion coefficients of these systems with filler content show the outstanding changes according to the filler size. The diffusion via free volume is dominant in the EMC with micro-sized filler; however, the diffusion with the interaction of absorption according the increase of the filler surface area is dominant in the EMC with nano-sized filler.

• Journal of Bio-Environment Control
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• v.29 no.2
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• pp.202-208
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• 2020

The objective of this study was to select the right species among Agastache in the family Lamiaceae as the result of growth analysis and functional substance analysis. Among 22 species of Agastache, five species (Agastache cana, Agastache foeniculum, Agastache rugosa 'Spike Blue', Agastache rugosa 'Spike Snow', Agastache rupestris) were selected by referring to United States Department of Agriculture (USDA)'s plant hardiness zone area and Korea's one based on USDAs. These plants were cultured at 24 ± 1℃ and 18 ± 1℃ (day and night temperatures, respectively) and 65 ~ 75% relative humidity in a hydroponic culture system for 4 weeks. In terms of growth analysis experiment, stem length, root length, leaf width, leaf area, leaf number, SPAD value, and fresh and dry weights of shoots and roots were measured. The results showed that A. rugosa SS and A. rugosa SB have a higher overall balance value than other species. When compared functional substance value (rosmarinic acid, tilianin, and acacetin) of five species, A. rugosa SS and A. rugosa SB are significantly higher than other species in Agastache. It seems to be directly proportional to the growth analysis results. When considering the growth and functional substance part comprehensively, A. rugosa SS and A. rugosa SB are the most optimal high-value species among Agastache.

• Journal of Korea Foresty Energy
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• v.21 no.3
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• pp.34-45
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• 2002

This study was carried out to investigate the diversity and frequency of ectomycorrhizal fungi by cutting levels in Quercus acuta and Pinus densiflora stands from June to October, 2001. The obtained results from investigation were as follows, 1. The total of fungi found during the surveyed periods were 50 species, 30 genus, 15 families. The fungi belonged to Agaricales(37 species, 18 genus, 7 families), Aphllophorales(7 species, 6 genus, 3 families), Auriculariales(1 species, 1 genus, 1 families) and Gasteromycetes(5 species, 5 genus, 4 families), Basidiomycota. 2. The total number of putative ectomycorrhizal fruiting bodies were 137 individuals, 22 species, 10 genus, 5 families, 79 individuals, 10 species, 6 genus, 3 families at strip-cutting area of Pinus densiflora stand, 24 individuals, 9 species, 5 genus, 4 families at strip-cutting area of Quercus acuta stand and 25 individuals, 10 species, 4 genus, 3 families at spacing cutting area of Quercus acuta stand. 3. Tylropilus neofelleus had high host specificity associated with Chamaecyparis obtusa, while Amanita pseudoporphyria had relatively wide host ranges compared to other ectomycorrhizal fungi. 4. The results analyzed by Correlation coefficients showed that relative humidity and precipitation were major enviromental factors to affect the distribution of ectomycorrhizal fruiting bodies.

• Korean Journal of Agricultural Science
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• v.24 no.2
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• pp.132-137
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• 1997

Effective storage facilities are required to stabilize the price of agricultural and marine products to preserve their qualities due to the big fluctuation of shrimp price in Korea. It is easy to make the cave because of good conditions of the land configuration, soil and convenient transportation. The cave storage can save the cost about 40% in building site and equipment, and about 50% in maintenance comparing to existing low temperature storage facilities. The cave storage provide to improve the quality of their stored products with the low heat conductivity, the constant temperature and humidity year round. Therefore, more low temperature storage facilities are required because the items are expanded from potatoes, sweet potatoes, onions, garlics, apples and chestnuts to tangerines, grapes, cabbages, radishes, and wet ginsengs. The demands of the low temperature storage facilities can be substituted into the cave storage facilities. Thus, studies are conducted to observe the changes of the components of the pure and the seasoned salted shrimps with fermentation period during stored at room temperature in cave and to establish the storing at underground facilities to produce high quality salted fish to make profit.

• Journal of Preventive Medicine and Public Health
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• v.27 no.3 s.47
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• pp.505-516
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• 1994

For the purpose of preparing the fundamental data on air pollution in underground shopping center and also contributing to the health improvement of residents, the authors measured the level of $SO_2,\;NO_2,\;TSP,\;CO,\;CO_2$ and also some related factors as air temperature, air movement, relative humidity and mean radiation temperature at inside and outside of underground shopping center in Pusan from January to February and from July to August 1994. The results were as follows : 1. The mean concentration of CO within the underground shopping center was $3.1{\pm}1.3ppm$ in winter and $2.1{\pm}0.9ppm$ in summer. There was a negative correlation (p<0.01) between inner CO concentration and temperature in summer and no correlation between inner CO concentration and outer CO concentration in underground shopping center 2. The mean concentration of COE within the underground shopping center was $876{\pm}353ppm$ in winter and $757{\pm}125ppm$ in summer. There was a negative correlation (p<0.01) between inner $CO_2$ concentration and air movement in summer and positive correlation (p<0.05) between inner $CO_2$ concentration and outer $CO_2$ concentration in underground shopping center. 3. The mean concentration of $SO_2$ within a underground shopping center was $0.036{\pm}0.019ppm$ in winter and $0.040{\pm}0.013ppm$ in summer. There was a positive correlation(p<0.01) between inner $SO_2$ concentration and temperature in summer and positive correlation between inner $SO_2$ concentration and outer $SO_2$ concentration in summer and winter in underground shopping center. 4. The mean concentration of $NO_2$ within a underground shopping center was $0.052{\pm}0.038ppm$ in winter and $0.042{\pm}0.016ppm$ in summer. There was a no correlation between inner $SO_2$ concentration and thermal factors in summer and winter and low correlation between inner $SO_2$ concentration and outer $SO_2$ concentration in underground shopping center 5. The mean concentration of TSP within a underground shopping center was $430{\pm}214{\mu}g/m^3$ in winter, $366{\pm}73{\mu}g/m^3$ in summer, and very in excess of the atmospheric environmental quality standards of Korea ($150{\mu}g/m3{\downarrow}$). There was low correlation between inner TSP concentration and temperature in summer and high correlation between inner TSP concentration and outer TSP concentration in underground shopping center.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.465-471
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• 2001

The effect of sintering condition on the mechanical properties and leachability of polydispersed ceramic core body made by gel-casting process in aqueous medium have been investigated. The polydispersed ceramic slip that has low viscosity($\leq$1000cP, at 1000cP (at $50sec^{-1}$ ) and high solid loading(50vo1%) was obtained. The green bodies were fabricated through casting and gelation at room temperature followed by drying at $25^{\circ}C$for 48hrs under relative humidity of 80%. Crack-free green body was successfully fabricated through the above process. The strength at room temperature, apparent bulk density, and shrinkage of the ceramic core body increased propotionally with increasing sintering temperature(1100~150$0^{\circ}C$). However, porosity of the ceramic core body showed relatively low vague. Leaching rate of sintered core body increased with increasing porosity of the sintered body, and was significantly dependent upon the concentration of alkali caustic solution at the same leaching temperature.