• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.1
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• pp.66-71
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• 2004

Airborne contaminant particles are intruded into optical disk drive(ODD) due to the flow caused by disk rotation and can be adhered to objective lens, which causes read/write errors. Such a phenomenon can be a serious problem for high-density storage devices. The purpose of this paper is to understand the effect of particle contamination of objective lens in a CD-ROM drive on laser diode power and photo diode RF signal. The measurements of laser power and readout RF signal were carried out by using a laser power meter and a time interval analyzer, respectively. The parameters for estimating a readout-signal' distortion were its jitter and amplitude. Alumina(Al$_2$O$_3$) particles were used as test dust particles. The results show that the failure for data access happened as the degree of lens contamination was greater than 20％.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2227-2232
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• 2011

The new metrology, Advanced Poly-silicon Ultra-Trace Profiling (APUTP), was developed for measuring bulk Cu and Ni in heavily boron-doped silicon wafers. A Ni recovery yield of 98.8% and a Cu recovery yield of 96.0% were achieved by optimizing the vapor phase etching and the wafer surface scanning conditions, following capture of Cu and Ni by the poly-silicon layer. A lower limit of detection (LOD) than previous techniques could be achieved using the mixture vapor etching method. This method can be used to indicate the amount of Cu and Ni resulting from bulk contamination in heavily boron-doped silicon wafers during wafer manufacturing. It was found that a higher degree of bulk Ni contamination arose during alkaline etching of heavily boron-doped silicon wafers compared with lightly boron-doped silicon wafers. In addition, it was proven that bulk Cu contamination was easily introduced in the heavily boron-doped silicon wafer by polishing the wafer with a slurry containing Cu in the presence of amine additives.

• Journal of Korean Biological Nursing Science
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• v.10 no.2
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• pp.131-140
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• 2008

Purpose: This study is about safety of the expressed human milk by investigating its bacterial contamination and antibiotic resistance of the microbes in the expressed milk. Methods: The data are collected from the 156 mothers and their newborn infants in NICU of U University Hospital from January 2004 to September 2005. Results: 1) The expressed human milk was contaminated by Staphylococcus epidermidis for 66.7%, Two mixed bacterial strain for 11.5%, Acinetobacter species for 8.0%, Klebsiella species for 4.6%, Staphylococcus aureus for 4.6%. 2) The microbes in the human milk had high resistance to the Antimicrobial agents: 77.5% for Penicillin-G, 66.6% for Oxacillin, and 63.7% for Cephalothin. 3) The distribution of microbes showed a significant depending on the place of the milk expression (p=.020). In particular, mixed bacterial strain was found more in the milks expressed at home than the milk expressed at the hospital. Conclusion: This study shows the importance of systematic education of feeding process in expressed milk: poor management of a breast pump, inadequate hand washing and imperfect breast cleaning explain the reasons of contamination 156 cases.

• Journal of Environmental Science International
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• v.25 no.1
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• pp.11-21
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• 2016

The soil contamination by heavy metals in playgrounds of kindergartens in Vilnius city is analysed in this article. The aim of this research is to investigate and evaluate soil contamination by heavy metals in playgrounds of kindergartens in different territories of Vilnius city. Concentrations of heavy metals were measured using Thermo Fisher Scientific Niton$^{(R)}$ XL2 X-ray fluorescence spectrometer. Maximum allowable and background concentrations that are given in Lithuanian hygiene standard and Lithuania geochemical atlas are used to compare and evaluate concentrations of heavy metals. Concentrations of heavy metals and their spatial distribution were analysed in order to exclude the most contaminated areas relating with different functional areas of the city. Geo-statistical analysis and maps of spatial distribution were developed using IDW interpolator in ArcMap software. Detail soil surveys helps to assess the extent of anthropogenic impact in different parts of the city which can be harmful to the soil ecosystem and human health. Such researches can help to change or select different function for city areas in territorial planning process.

• Journal of the Korean Geosynthetics Society
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• v.8 no.2
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• pp.1-9
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• 2009

When some structures are constructed over the sanitary landfill, the waste should be treated by means of replacement and other ways. Otherwise, various problems like a ground contamination, settlement, reduction of bearing capacity and others may be generated. To find out the optimal method of treatment, the properties of the ground have to be inspected. In this study, the preliminary investigation was conducted to find out the characteristic of this site which is considered as insanitary waste landfill. Furthermore, the shape and the amount of the waste was investigated by subsurface investigation like a boring and sampling methods. In addition, the degree of ground contamination and disposal method of refuse was examined.

• Advances in environmental research
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• v.6 no.3
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• pp.203-216
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• 2017

For survival of human beings clean water is an essential commodity whereas contamination in drinking water threatens to mankind. The main cause of water contamination is social and development activities of human being along with increasing population. The community in the study area has acute shortage of drinking water along with about 40 to 60% has no access to safe drinking water. This study indicates drinking water quality of two major sources of coastal belt of Karachi one is supplied by Karachi Water & Sewerage Board (KWSB) as tap water and the other through groundwater. The physicochemical analysis was carried out by following the standard methods for checking the quality of drinking water. The analyzed results showed that the quality of groundwater was unfit as potable water. The most critical situation was observed as high level of contamination followed by high turbidity and increased salinity levels. TDS in surface water were found 12% above and TDS in groundwater was 20% below the National Drinking Water Quality Standards (NDWQS) of Pakistan as well as the permissible WHO drinking water quality guidelines.

• Korean Journal of Adult Nursing
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• v.26 no.1
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• pp.98-106
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• 2014

Purpose: The purpose of this study was to explore the effect of glove changing during surgery for colon cancer on reducing the degree of contamination of surgical gloves. Methods: The randomized posttest control group design was used. Total 72 surgeries of colon cancer in the K University Hospital in Seoul performed by the team of A-Surgeon and B-Scrub nurse were randomly assigned to one of the three groups. Glove changing with single-gloved state was implemented in the Experimental Group I and outer glove changing with double-gloved state was executed in the Experimental Group II. Single-gloved state was carried in the Control Group. Following the surgical procedure, specimens for bacterial culture were collected the from scrub nurse's gloves to compare the degree of contamination among the three groups. Data were analyzed with One-way ANOVA and the Scheff$\acute{e}$'s multiple comparison test. Results: The degrees of contamination of the Experimental Group I and II were significantly lower than that of the Control Group. There was no significant difference between Experimental Group I and II. Conclusion: Glove changing during surgery with either single or double-gloved state is effective in reducing the degree of contamination of surgical gloves, therefore these methods should be utilized in clinical practice.

• Journal of Drive and Control
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• v.9 no.2
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• pp.39-45
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• 2012

The NAS 1638 cleanliness classification system was originally developed in 1966 by the US Aircraft Industries of America to both simplify reporting of particle count data and to control the introduction of dirt during the assembly of aircraft fluid systems. The numbers of particles at stated sizes are represented by broad bands where the interval was generally a doubling of contamination. A number of systems have been introduced since this to suit differing requirements. NAS 1638 and AS4059 are used in other industrial sectors such as the Off-shore & Sub-Sea and the Primary Metal Industries. The changes to ISO contamination measurement standards controlled by ISO/TC131/SC6 in 1999 meant that a revision of most of these classification systems was necessary. The body responsible for NAS 1638 decided to withdraw it for new installations and replace it with an update of an existing standard, SAE AS 4059. This paper details the philosophy behind the contamination coding systems, the reasons for the changes to the ISO contamination standards and explains the workings of AS 4059, the replacement for NAS 1638. It goes on to detail the latest changes to this standard.

• Journal of Microbiology and Biotechnology
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• v.5 no.6
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• pp.309-314
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• 1995

Samples were collected from a commercial ethanol production plant to enumerate the bacterial contamination in each step of a starch based ethanol production process. Though the slurry of raw material used in the process carried bacteria with various colony morphology in the order of $10^4$ per ml, only the colonies of white and circular form survived and propagated through the processes to the order of $10^8$ per ml at the end of fermentation. Almost all of the bacterial isolates from the fermentation broth were lactic acid bacteria. Heterofermentative Lactobacillus fermentum and L. salivarius, and a facultatively heterofermentative L. casei were major bacteria of an ethanol fermentation. In a batch fermentation L. fermentum was more detrimental than L. casei to ethanol fermentation. In a cell-recycled fermentation, ethanol productivity of 5.72 g $I^{-1} h^{-1}$ was obtained when the culture was contaminated by L. fermentum, whilst that of the pure culture was 9.00 g $1^{-1} h^{-1}$. Similar effects were observed in a cell-recycled ethanol fermentation inoculated by fermentation broth collected from an industrial plant, which showed a bacterial contamination at the level of 10$^8$ cells per ml.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.63-66
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• 2003

This study applied a hydrogeological field survey and isotope investigation to identify source locations and delineate pathways of groundwater contamination by nitrogen compounds. The infiltration and recharge processes were analyzed with groundwater-level fluctuation data and oxygen-hydrogen stable isotope data. The groundwater flow pattern was investigated through groundwater flow modeling and spatial and temporal variation of oxygen isotope data. Based on the flow analysis and nitrogen isotope data, source types of nitrate contamination in groundwater are identified. Groundwater recharge largely occurs in spring and summer due to precipitation or irrigation water in rice fields. Based on oxygen isotope data and cross-correlation between precipitation and groundwater level changes, groundwater recharge was found to be mainly caused by irrigation in spring and by precipitation at other times. The groundwater flow velocity calculated by a time series of spatial correlations, 231 m/yr, is in good accordance with the linear velocity estimated from hydrogeologic data. Nitrate contamination sources are natural and fertilized soils as non-point sources, and septic and animal wastes as point sources. Seasonal loading and spatial distribution of nitrate sources are estimated by using oxygen and nitrogen isotopic data.