• Journal of Surface Science and Engineering
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• v.32 no.3
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• pp.239-243
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• 1999

At Present, 200mm wafer technology is being applied for commercial fabrications of 64, 128, and 256 M DRAM devices, and 300mm technology will be evolved for 1G DRAM devices in the early 21th century, recognizing limitations of several process technologies. In particular recognition has been realized in harmful effects of surface contamination of trace metals introduced during devicing processes. Such a guide line for surface metal contamination has been proposed as 1E9 and 1E10 atoms/$\textrm{cm}^2$ of individual metal contamination for wafering and devicing of 1G DRAM, respectively, and so its measurement limit should be at least 1E8 atoms/$\textrm{cm}^2$. The detection limit of present measurement systems is 2E9 atoms/$\textrm{cm}^2$ obtainable with TRXFA(Total Reflection X-Ray Fluorescence Analysis). TRXFA is nondestructive and the simplest in terms of operation, and it maps the whole wafer surfaces but needs detection improvement. X-Ray intensity produced with synchrotron accelerator is much higher than that of conventional X-ray sources by order of 4-5 magnitudes. Hence theoretically its reactivity with silicon surfaces is expected to be much higher than the conventional one, realizing improvement of detection limit. X-ray produced with synchrotron accelerator is illuminated at a very low angle with silicon wafer surfaces such as 0.1 degree and reflects totally. Hence informations only from surface can be collected and utilized without overlapping with bulk informations. This study shows the total reflection phenomenon and quantitative improvement of detection limit for metallic contamination. It is confirmed that synchrotron X-ray can be a very promising alternative for realizing improvement of detection limit for the next generation devices.

• Journal of Korean Biological Nursing Science
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• v.21 no.2
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• pp.133-140
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• 2019

Purpose: The purpose of this study was to check the degree of residual microbial contamination after disinfection of reusable suction containers, used in an intensive care unit (ICU) and present basic data for efficient use through cost analysis in comparison to disposable suction containers. Methods: This study was conducted on 32 reusable suction containers used in an ICU on a selected specific day. After disinfection and washing, specimens were collected from the used containers and cultured to check for microbial contamination. Additionally, a comparative narrative study analyzes the cost of using reusable suction containers and disposable suction containers. Data were analyzed with the SPSS WIN 20.0 program using real numbers and percentage ${\chi}^2$-test. Results: As a result of the study, microorganisms were found in all samples where in 30 were gram-positive (62.5%) while 13 were gram-negative (27.1%). Based on level of contamination, microorganisms were less than 10CFU/ml in 18 samples (56.3%); 11-99CFU/ml in six samples (18.8%); and more than 100CFU/ml in eight samples (25%). Cost per day for a reusable suction container was $10,655+{\alpha}$ while cost per day for a disposable suction container was 10,666 won. Conclusion: This study found that reusable suction containers, even after disinfection, accounted for factors of potential infection as well as microbial contamination. So, disposable suction containers are superior in cost-effectiveness and highly efficient for use with infected patients.

• Biomedical Science Letters
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• v.28 no.4
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• pp.317-321
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• 2022

Due to COVID-19 pandemic, wearing face masks is obligatory to prevent respiratory virus transmissions in the community. However, there are few studies of the desirable number of wearing a face mask, and how to store them for reuse. Therefore, in this study, a survey was conducted among 208 healthy adults, and 27 kf-94 masks worn for 1, 2, and 3 days were collected. To estimate the risk of bacterial contamination, we analyzed the extent of bacterial contamination of the BHI medium and 16S rRNA gene sequencing. With an increase in the number of days of using the mask, the degree of bacterial contamination of the used mask gradually increased. As a result of 16S rRNA PCR performed for strain identification, Staphylococcus, known as a pathogenic bacterium, was identified the most. In conclusion, we found that wearing a cotton KF mask provides an optimal environment for microbes, which are related to the skin and respiratory system, to thrive. Therefore, it is also important to reduce the risk of bacterial infection of the face mask with appropriate sterilization methods.

• The Journal of Engineering Geology
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• v.15 no.1
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• pp.29-39
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• 2005

For detecting a ground contamination survey, soil sampling method have been used a drilling or coring technique in general. However these methods are very difficult to systematically real-time monitoring of variation of contamination degree in field. ]'n this research frequency Domain Reflectometry (FDR) system was suggested and carried out to experimental approaches for determination of oil contamination on surface and underground. Experimental method using FDR method was discussed with feasibility of measurement in the laboratory column test. It is determined to degree of oil contamination due to response of dielectric constant re-lated with volumetric water content(θ/sub w/) and volumetric oil content( θ/sub al/ ) of saturated and unsaturated soil media. And physical properties such as effective porosity and oil residual ratio of saturated soil media were also measured through real-time monitoring works using installed FDR measurement sensors, which are defected characteristics of oil movement in the saturated soil media under the soil column tests. In the results of these experiments, a range of effective porosity was estimated to about 0.35 compared with initial porosity 0.40 of manufactured saturated soil media, which is also calculated to about 87.5% to the ratio of initial porosity to effective porosity. Finally oil residual ratio which is compared with volumetric water content and volumetric oil content was calculated about 62.5%.

• Korean Journal of Food Science and Technology
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• v.48 no.5
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• pp.525-529
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• 2016

Twenty-nine pepper products commercially available in the market were collected and investigate for contamination levels. Pepper products purchased from traditional markets had a degree of contamination of $10^6-10^7CFU/g$ aerobic bacteria, $10^4-10^5CFU/g$ Bacillus sp., and less than $10^2CFU/g$ yeast and molds. Organic pepper showed a degree of contamination of $10^4$ aerobic bacteria, $10^2-10^3$ Bacillus sp., and less than $10^1$ yeast and molds. Intense pulsed light (IPL) treatment of 10 min (1,000 V, 5 pps and 4 cm sample-to-lamp distance) showed a bacterial death rate of 1.45-1.55 log for whole peppers, and of 0.8-0.85 log for black and white pepper powder. The sterilization rate using IPL was higher than that using other non-thermal sterilization methods, such as ozone treatment or low-pressure discharge plasma sterilization, indicating that the IPL sterilization method may find potential application in the industry. However, further studies may need to be conducted to enhance the effect of sterilization.

• Economic and Environmental Geology
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• v.55 no.6
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• pp.717-726
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• 2022

This study was conducted to assess the geochemical contamination degree of As, Cd, Cu, Pb, Sb, and Zn in the soil and water samples from an abandoned gold mine. Enrichment Factor (EF), Geoaccumulation Index (Igeo), and Pollution Load Index (PLI) were carried out to assess the geochemical contamination degree of the soil samples. Variations of sulfate and heavy metals concentration in water samples were determined to identify the geochemical distribution with respect to the distance from the mine tailing dam. Geochemical pollution indices indicated significant contaminated with As, Cd, Pb, and Zn in the soil samples that areas close to the mine tailing dam, while, Sb showed similar indices in all soil samples. These results indicated that the As, Cd, Pb, and Zn dispersion has occurred via anthropogenic sources, such as mining activities. In terms of water samples, anomalies in the concentrations of As, Cd, Zn, and SO₄^2- was determined at specific area, in addition, the concentrations of the elements gradually decreased with distance. This result implies the heavy metals distribution in water has carried out by the weathering of sulfide minerals in the mine tailing and soil. The study area has been conducted the remediation of contaminated soil in the past, however, the geochemical dispersion of heavy metals was supposed to be occurred from the potential contamination source. Therefore, continuous monitoring of the soil and water is necessary after the completion of remediation.

• Journal of the Mineralogical Society of Korea
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• v.19 no.3 s.49
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• pp.171-187
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• 2006

The status of heavy metal contamination was investigated using chemical analyses of stream waters and sediments obtained from Samsanjeil and Sambong Cu mining area in Goseong-gun, Gyeongsangnam-do. In addition, the degree and the environmental risk of heavy metal contamination in stream sediments was assessed through pollution index (Pl) and danger index (DI) based on total digestion by aqua regia and fractionation of heavy metal contaminants by sequential extraction, respectively. Not only the degree of heavy metal contamination was significantly higher in Samsanjeil area than in Sambong area, but its environmental risk was also revealed much more serious in Samsanjeil area than in Sambong area. The differences in status and level of contamination and environmental risk between both two mining areas may be attributed to existence of contamination source and geology. Acid mine drainage is continuously discharged and flows into the stream in Samsanjeil mining area, and it makes the heavy metal contamination in the stream more deteriorated than in Sambong mining area in which acid mine drainage is not produced. In addition, the geology of Samsanjeil mining area is mainly comprised of andesitic rocks including a small amount of calcite and having lower pH buffering capacity fer acid mine drainage, and it is likely that the heavy metal contamination cannot be naturally attenuated in streams. On the contrary, the main geology of Sambong mining area consists of pyroclastic sedimentary Goseong formation containing a high content of carbonates, particularly calcite, and it seems that these carbonates of high pH buffering capacity prevent the heavy metal contamination from proceeding downstream in stream within that area.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.4 s.15
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• pp.21-26
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• 2004

It is muck important to determine the intercepting capacities as measures for reducing the load of contamination influenced by CSOs during wet weather period. Intercepting and treating the whole rainfalls can be best measured for reducing the contamination load, but it is not desirable in view of scale and preservation of the wastewater treatment facilities. This study analyzed the quantity and quality of the water in the combined sewer by method of changing the type and size of drainage basin and intercepting capacities in rainfalls, estimate the influence the other CSOs at the change of planned intercepted quantity, and compared the degree of contamination load between the combined system and separate system by examining the influence of the other CSOs at the change of planned intercepted quantity.

• Economic and Environmental Geology
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• v.29 no.1
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• pp.57-63
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• 1996

The Dalsung copper-tungsten mine in the Taegu area, Korea was closed in 1975 and may be the sources of the heavy metal contamination in the tributary system and soil-plant system due to the mine drainage derived from the mine wastes and tailings. To examine the degree and extent of heavy metal contamination in the vicinity of Dalsung mine area, stream water and soil samples were taken and analyzed for heavy metals by ICP-AES and AAS. Highly contaminated soils are found near the Lower Tunnel No.0 ranging up to $1760{\mu}g/g$ As, $2060{\mu}g/g$ Cu, $1120{\mu}g/g$ Pb and 346 ${\mu}g/g$ Zn. From the results of the sequential extraction methods for the metal speciation, the heavy metals in soils may be derived from soil parent materials and acid mine drainage. With the processes for the heavy metal removal, most of the heavy metal ions in the acid mine drainage are removed by being exchanged with Ca ions held by the bentonite, hydroxyapatite and calcium hydoxide.

• Journal of Environmental Impact Assessment
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• v.13 no.5
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• pp.251-262
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• 2004

In order to investigate the geochemical characteristics of surface sediments in lower Yeongsan river system, sediment samples from the main stream of Yeongsan river, Gomakwon and Hampyeong streams were collected and analyzed for grain size and metal and organic carbon contents. The sediment types of the streams widely vary from pebble to mud. The metal contents in the sediments are mainly dependent on grain size of the sediments, geology around the streams and organic matter contents from the domestic sewage. Enrichment factor (EF) representing the degree of metal contamination in the sediments are relatively low in the study area. But, high Zn and Pb values seem to be from the study area, partly.