• Food Science of Animal Resources
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• v.38 no.2
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• pp.282-290
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• 2018

This research was to evaluate microbial contamination levels in meat samples at hazard analysis critical control point (HACCP)-implemented processing plants that produce beef, pork, and chicken. During a period of about a year, a total of 178 samples (76 from beef, 89 from pork, and 13 from chicken) were obtained from raw materials (21.3%) and final products (78.7%). All samples were determined for each 25 g homogenized one. Samples were analyzed to determine the total aerobic plate count (APC), coliform count (CC), and E. coli count (ECC). By month, APC levels were the highest in September and the lowest in February (p<0.001). In comparison among season, APC levels in meat samples were the highest in the summer and the lowest in winter (p<0.001). By month, the highest CC prevalence was found in August, followed by October and then July (p<0.001). By season, the highest CC was obtained in summer, followed by autumn and then spring (p<0.001). All samples were negative for ECC. There was a direct correlation between the product form and coliform presence (p<0.001). In addition, there was a positive correlation between the APC and CC (r=0.261). The APCs in analyzed samples ranged from below <$10^1CFU/g$ to <$10^7CFU/g$. In conclusion, the month and season had significant effects on microbial contamination levels at HACCP implemented processing plants. Interrelationships between (i) the product form and coliform, (ii) the APC and CC were revealed.

• Journal of Astronomy and Space Sciences
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• v.12 no.2
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• pp.234-243
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• 1995

Korea's third rocket, which is currently under development for launch in 1997, is expected to reach as high as 160km and thus, it will provide a good opportunity for the direct measurement of the plasmas in the E-region ionosphere of the Korean peninsula. Langmuir probe techniques, which are the basic tools of the plasma experiment, may yield inaccurate results if they are applied in the conventional form as they are used in the laboratory experiments because of the contamination. In the present paper we study the contamination problem by performing the ground experiments in the vacuum chamber using the contaminated probe. The result show that the contamination effect is reduced when the plasma density is low or when the frequency of the sweep voltage is fast. We propose a modified Langmuir probe based upon our experiments which is suitable for the rocket experiments.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.203-209
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• 2019

A number of industrial zones in South Korea were reported contaminated by heavy metals. Such contamination could cause severe damage to the subsurface environment including soil and groundwater. The treatment of zeolite mixing with soil at the bottom of such industrial zones might prevent, or at least reduce the damage of contamination by adsorption of the heavy metals from the leakage. However, such mixtures should maintain the proper bearing capacity as a foundation fill material from the geotechnical point of view at the same time. To investigate the effect of mixtures of zeolite with local soils for the adsorption of heavy metals (Zn, Pb) and sustainability of bearing capacity, adsorption isotherm tests and direct shear test with compaction tests were performed. Results showed that the mixing zeolite with local soils effectively reduces the spreading of the heavy metal contamination when maintaining its proper geotechnical properties as a fill material of industrial zones.

• The Journal of the Convergence on Culture Technology
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• v.9 no.2
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• pp.561-568
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• 2023

Various defects occur in concrete structures due to internal and external environments. If there is a defect, it is important to efficiently identify and maintain it because there is a problem with the structural safety of concrete. However, recent deep learning research has focused on cracks in concrete, and studies on exfoliation and contamination are lacking. In this study, focusing on exfoliation and contamination, which are difficult to label, four models were developed and their performance evaluated through unlabelling method, filtering method, the convergence of transfer learning based k-means clustering. As a result of the analysis, the convergence model classified the defects in the most detail and could increase the efficiency compared to direct labeling. It is hoped that the results of this study will contribute to the development of deep learning models for various types of defects that are difficult to label in the future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.310-313
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• 2002

Structures obtained with a direct boning of two FZ silicon wafers joined in such a way that a smooth surface of one wafer was attached to the grooved surface of the other were studied. A square net of grooves was made with a conventional photo lithography process. After high temperature annealing the appearance of voids and the rearrangement of structural defects were observed with X-ray diffraction topography techniques. It was shown that the formation of void free grooved boundaries was feasible. In the cases when particulate contamination was prevented, the voids appeared in the grooved structures could be eliminated with annealing. Since it was found that the flattening was accompanied with plastic deformation, this deformation was suggested to be intensively involved in the process of void removal. A model was proposed explaining the interaction between the structural defects resulted in "a dissolution" of cavities. The described processes may occur in grooved as well as in smooth structures, but there are the former that allow to manage air traps and undesirable excess of dislocation density. Grooves can be paths for air leave. According to the established mechanisms, if not outdone, the dislocations form local defect arrangements at the grooves permitting the substantial reduction in defect density over the remainder of the interfacial area.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.753-759
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• 2000

Photoelectric charging is a very efficient way of charging small particles. This method can be applied to combustion measurement, electrostatic precipitator, metal separation and control of micro-contamination. To understand the photoelectric charging mechanism, particle charging of silver by exposure to ultraviolet is investigated in this study. Average charges and charge distributions are measured at various conditions, using two differential mobility analyzers, a condensation nucleus counter, and an aerosol electrometer. The silver particles are generated in a spark discharge aerosol generator. After that process, the generated particles are charged in the photoelectric charger using low-pressure mercury lamp that emits ultraviolet having wavelength 253.7 nm. The results show that ultra-fine particles are highly charged by the photoelectric charging. The average charges linearly increase with increasing particle size and the charge distribution change with particle size. These results are discussed by comparison with previous experiments and proposed equations. It is assumed that the coefficient of electron emission probability is affected by initial charge. The results also show that the charge distribution of a particle is dependent on initial charge. Single changed particle, uncharged particle and neutralized particle are compared. The differences of charge distribution in each case increase with increasing particle size.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.6
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• pp.801-806
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• 2004

The pilot study was conducted to (i) investigate the ability of various membrane integrity monitoring methods to detect changes in membrane integrity during operation, and (ii) determine the impact of membrane damage on microbial removal by microfiltration. Two variations of air pressure hold tests were investigated for direct integrity monitoring: pressure decay (PD) and diffusive air flow (DAF) tests which are most commonly used integrity tests for microfiltration (MF) membranes. Both PD and DAF tests were sensitive enough to detect one damaged fiber out of 66,000 under field operaing conditions. Indirect integrity monitoring such as turbidity and particle counting, however, responded poorly to defects in membrane systems. Microbial challenge study was performed using both new and deliberately damaged membranes, as well as varying the state of fouling of the membrane. This study demonstrated that MF membrane with nominal pore size $0.2{\mu}m$ was capable of removing various pathogens including coliform, spore, and cryptosporidium, at the level required by drinking water regulations, even when high operating pressures were applied. A sharp decrease in average log reduction value (LRV) was observed when one fiber was damaged, emphasizing the importance of membrane integrity in control of microbial contamination.

• Journal of Microbiology
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• v.44 no.2
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• pp.162-170
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• 2006

Oysters are known to be carriers of food-born diseases, but research on viruses in Korean oysters is scarce despite its importance for public health. We therefore tested oysters cultivated in Goheung, Seosan, Chungmu, and Tongyeong, for viral contamination using cell culture and integrated cell culture PCR (ICC-PCR) with Buffalo green monkey kidney (BGMK) and human lung epithelial (A549) cells. Additional screens via PCR, amplifying viral nucleic acids extracted from oysters supplemented our analysis. Our methods found 23.6 %, 50.9 %, and 89.1 % of all oysters to be positive for adenoviruses when cell culture, ICC-PCR, and direct PCR, respectively, was used to conduct the screen. The same methodology identified enteroviruses in 5.45%, 30.9%, and 10.9% of all cases. Most of the detected enteroviruses (81.3%) were similar to poliovirus type 1; the remainder resembled coxsackievirus type A1. A homology search with the adenoviral sequences revealed similarities to adenovirus subgenera C (type 2, 5, and 6), D (type 44), and F (enteric type 40 and 41). Adenovirus-positive samples were more abundant in A549 cells (47.3%) than in BGMK cells (18.2 %), while the reverse was true for enteroviruses (21.8 % vs. 14.5 %). Our data demonstrate that Korean oysters are heavily contaminated with enteric viruses, which is readily detectable via ICC-PCR using a combination of A549 and BGMK cells.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3279-3281
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• 1999

This paper describes a method of direct wafer bonding using surfaces activated by a radio-frequency hydrogen plasma. The hydrogen plasma cleaning of silicon in the RIE mode was investigated as a pretreatment for silicon direct bonding. The cleaned silicon surface was successfully terminated by hydrogen, The hydrogen-terminated surfaces were rendered hydrophilic, which could be wetted by Dl water rinse. Two wafers of silicon and silicon dioxide were contacted to each other at room temperature and postannealed at $300{\sim}1100^{\circ}C$ in an $N_2$ atmosphere for 2 h. From the AFM results, it was revealed that the surface became rougher with the increased plasma exposure time and power. The effect of the plasma treatment on the surface chemistry was investigated by the AES analysis. It was shown that the carbon contamination at the surface could be reduced below 5 at %. The interfacial energy measured by the crack propagation method was 122 $mJ/m^2$ and 384 $mJ/m^2$ for RCA cleaning and hydrogen plasm, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.287-292
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• 2012

This study was to build the database by collecting the results of legal leak test and self-test conducted by the owners of soil contamination facilities at soil-related specialized agency to grip objective status on soil contamination facilities and evaluate classification results. The results of the study showed that the unsuitable rate of business unit is 53.6%, the business with leak that could cause actual pollution is 25.7%, the unsuitable rate of the voluntary self-test is 57.3%, that of the compulsory inspection is 17.2% depending on the test motivation, that of the direct-test is 58.9%, and that of the indirect-test is 22.5% depending on the test methods. There was a significant difference between the test motivation conducted and the test methods applied. From the results of the unsuitable reasons obtained we could assume that about 20% of the whole target tanks became potential sources with natural defects occurred when such tanks were made, and 2.2% of the whole tankers examined that persisting period was caused by progressing corrosion below the minimum thickness.