• Journal of the Korean Society of Tobacco Science
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• v.7 no.1
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• pp.57-65
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• 1985

This study was conducted to obtain the information for the difference of chemical characteristics in each tobacco growing districts and year. The results obtained were as follows 1. Difference of chemical characteristics in 6 districts: In case of flue-cured tobacco leaves, the produced leaf tobacco from Cheong Ju and Dae Jeon districts showed middle level in nicotine and total sugar contents, on the other hand, low nicotine and high sugar contents tobacco leaves were produced in An Dong and Jin Ju districts and high nicotine and low sugar contents of tobacco leaves in Su Won and Chun Cheon , respectively. In Burley tobacco leaves, the nicotine and total nitrogen contents of Chun Cheon districts product's were lower than those of Dae Jeon , Jeon Ju and Kwang Ju district's one. 2. Comparison of each tobacco produced year : The nicotine contents of five-cured and Burley tobacco leaves were the highest in 1981 and 1979, respectively. Also, as time goes to recent year, nicotine and total nitrogen contents were decreased and total sugar contents somewhat was increased .

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.172-176
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• 1996

The rapid structural change of ULSI chip includes minimum features, multilevel interconnection and large diameter wafers. Demands for the advanced chip structure necessitates the development of enhanced deposition, etching and planarization techniques. Planarization refers to a process that make rugged surfaces flat and uniform. One of the emerging technologies for planarization is chemical mechanical polishing(CMP). Chemical and mechanical removal actions occur during CMP, and both appear to be closely interrelated. The purpose of this study is the optimal application of the slurry to the various types of device materials during CMP. We investigates the effect of slurry on CMP characteristics for thermal oxide and sputtered Al blanket wafers. Results from the polishing rate and the uniformity of residual film include mechanical and chemical reactions between several set of slurry and work material.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1196-1197
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• 2006

FePt binary-alloy nanopowder has been successfully synthesized by chemical vapor condensation process with two metal organic precursors, i.e., iron pentacarbonyl and platinum acetylacetonate. Average particle size of the powder was less than 50 nm with very narrow size distribution, revealing high dispersion capability. Characteristics of the powder could be controlled by changing process parameters such as reaction temperature, chamber pressure, as well as gas flow rate. Magnetic properties of the synthesized FePt nanopowder were investigated and analyzed in terms of the powder characteristics.

• Journal of the Korean Chemical Society
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• v.13 no.1
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• pp.56-61
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• 1969

By the chemical procedure and infra-red spectroscopy, the characteristics of humic acid were studied. The results were as follows: 1. Molecular weight. 5,200. 2. Molecular formula. $C_{240}H_{250}O_{120}N_{1O}$. 3. Rational formula. 4. Confirmation of the accurate structure of humic acid is beyond us nowadays. The structure is speculated that it may be a kind of condensed polymer of many benzene kerns in which above mentioned various functional groups are attached. Also some part of the large quantities of oxygen would be furan type carbonyl and aliphatic ethereal forms.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.45-57
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• 2015

Objectives: This study aims to compare the physicochemical characteristics, toxicological data with Occupational Exposure Limits (OELs) of chemicals under the Occupational Safety and Health Act(OSHA) regulated by the Ministry of Employment and Labor of Korea. Methods: Information on chemicals which have OELs on physicochemical characteristics and toxicological data was collected using Material Safety Data Sheet(MSDS) from Korea Occupational Safety and Health Agency(KOSHA) and the Korea Information System for Chemical Safety Management(KISChem) in 2014. Statistical analyses including correlation and simple regression were performed to compare the OELs with chemical characteristics including molecular weight, boiling point, odor threshold, vapor pressure, vapor density, solubility and octanol-water partition coefficient(OWPC) and toxicological data such as median lethal dose($LD_{50}$) and median lethal concentration($LC_{50}$). Results: A total of 656 chemicals have OELs under OSHA in Korea. The numbers of chemicals which have eight-hour time weighted average(TWA) and short term exposure limits(STEL) are 618 and 190, respectively. TWA was significantly correlated with boiling point and STEL was only correlated with vapor pressure among physicochemical characteristics. Solubility and OWPC between "skin" and "no skin" substances which indicate skin penetration were not significantly different. Both $LD_{50}$ and $LC_{50}$ were correlated with TWA, while the $LC_{50}$ was not with STEL. As health indicators, health rating and Emergency Response Planning Guidelines(ERPG) rating as recommended by the National Fire Protection Association(NFPA) and American Industrial Hygiene Association(AIHA) were associated with OELs and reflect the chemical hazards. Conclusions: We found relationships between OEL and chemical information including physicochemical characteristics and toxicological data. The study has an important meaning for understanding present regulatory OELs.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.16-22
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• 2018

Silicon carbide (SiC) is used in various semiconductor processes because it has superior thermal, mechanical, and electrical characteristics as well as higher chemical and corrosion resistance than existing materials. Due to these characteristics, various manufacturing technologies have been developed for SiC. A recent development among these technologies is Chemical Vapor Deposition SiC (CVD-SiC). Many studies have been carried out on the processing and manufacturing of CVD-SiC due to its different material characteristics compared to existing materials like RB-SiC or Sintered-SiC. CVD-SiC is physically stable and has excellent chemical and corrosion resistance. However, there is a problem with increasing the thickness, because it is manufactured through a deposition process. Additionally, due to its high strength and hardness, it is difficult to subject to machining.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.218-218
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• 2003

• 한국전기화학회:학술대회논문집
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• 2000.04a
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• pp.33-33
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• 2000

• Polymer Science and Technology
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• v.18 no.1
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• pp.20-25
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• 2007

• Proceedings of the Zoological Society Korea Conference
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• 1996.10a
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• pp.105.2-105
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• 1996

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