• Korean Journal of Veterinary Service
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• v.37 no.4
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• pp.253-261
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• 2014

Porcine circovirus disease (PCVD) is a major problem of swine industry worldwide, and diagnosis of PCV2, causal agent of PCVD, has been doing in clinical laboratories of pig disease by polymerase chain reaction (PCR) methods. But the PCR analyses have a serious problem of misdiagnosis by contamination of DNA, in particular, from carryover contamination with previously amplified DNA or extracted DNA from field samples. In this study, an uracil DNA glycosylase (UNG)-based direct PCR (udPCR) without DNA extraction process and DNA carryover contamination was developed and evaluated on PCV2 culture and field pig samples. The sensitivity of the udPCR combined with dPCR and uPCR was same or better than that of the commercial PCR (cPCR) kit (Median diagnostics, Korea) on PCV2-positive serum, lymph node and lung samples of the pigs. In addition, the udPCR method confirmed to have a preventing ability of mis-amplification by contamination of pre-amplified PCV2 DNA from previous udPCR. In clinical application, 170 pig samples (86 tissues and 84 serum) were analysed by cPCR kit and resulted in 37% (63/170) of positive reaction, while the udPCR was able to detect the PCV2 DNA in 45.3% (77/170) with higher sensitivity than cPCR. In conclusion, the udPCR developed in the study is a time, labor and cost saving method for the detection of PCV2 and providing a preventing effect for DNA carryover contamination that can occurred in PCR process. Therefore, the udPCR assay could be an useful alternative method for the diagnosis of PCV2 in the swine disease diagnostic laboratories.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.3
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• pp.5-10
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• 2004

Electric contacts serve the purpose of transmitting electric signals across two conducting components. In this paper, the effects of contact conditions such as surface roughness, oxidation, and contamination were investigated with respect to electrical resistance variation of a connector in a direct current circuit. Such change in the electrical resistance is particularly important for low power circuits. The experimental results showed that compared with the effects of contact surface scratch or oxidation, the effect of contamination on the resistance variation was the most significant. In order to minimize failure due to electrical resistance change at the contact region, proper sealing to prevent contamination from entering the interface is needed.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.988-992
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• 2006

In recent semiconductor manufacturing clean rooms, air washers are used to remove airborne gaseous contaminants such as $NH_3,\;SO_x$ and organic gases from outdoor air introduced into clean room. Meanwhile, there is a large quantity of exhaust air from clean room. It is desirable to recover heat from exhaust air and use it to reheat outdoor air. In the present study, an experiment was conducted to investigate the heat recovery and gas removal efficiencies of a direct atomization type heat recovery air washer.

• Journal of Soil and Groundwater Environment
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• v.16 no.6
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• pp.106-112
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• 2011

This study developed preliminary assessment methodology for priority listing of soil and groundwater contamination sources, considering source characteristics, local environments and risk receptors. Source characteristics were evaluated by scoring relative risk of contamination sources. Local environments were evaluated by scoring annual rainfall, hydraulic conductivity of aquifer, and annual groundwater use. Risk receptors were evaluated by scoring local population, direct distance to surface water, direct distance to drinking-water wells. Scores of each parameter were allocated by analysing distribution of parameter values obtained from government databases. Distributed scores of source characteristics local environments: risk receptors were 12 : 12 : 12. The preliminary assessment scored 0 to 36 for each soil and groundwater sources. Inventory of soil and groundwater sources consisted of 7 categories. This study applied the preliminary assessment methodology to Manan-Gu, Anyang City, Korea. The number of car repair and washing facility was the largest in the contamination source inventory. Petroleum storage facilities showed the highest assessment score. The preliminary assessment methodology also indicated that Anyang-Dong was the priority section among Anyang-Dong, Suksu-Dong, Bakdal-Dong. This study is the first trial for relative ranking soil and groundwater contamination sources by considering source and local characteristics. Therefore, further researches and revision of the preliminary assessment methodology need to be pursued for various applications.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.2
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• pp.400-420
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• 1998

We already know that it is very difficult to obtain an "isolated field" for direct bonding during the surgical exposure of unerupted teeth. The aim of this in-vitro study is to simulate the clinical situation of forced eruption and to evaluate the tensile strengths of preligatured button with several types of contamination which can happen during the surgical exposure of unerupted teeth. Four orthodontic direct bonding systems were used. ($Ortho-One^{TM}$, $Rely-a-Bond^{(R)}$, $Ortho-Two^{TM}$, Phase $II^{(R)}$) Each material was divided into four groups(n=20) : Group 1. (Control, no contamination), Group 2. (Rinse etching agent with saline instead of water), Group 3. (Blood contamination of etched surface for 30 seconds), Group 4. (Blood contamination of primed surface for 30 seconds) 320 bovine anterior permanent teeth were divided into the above mentioned 16 groups. Enamel surface was flattened and ground under water coolant. Pre-ligatured buttons were prepared to the same form. (Cut 0.25 ligature wire 10 cm in length. Twist the ligature wire 30 times clockwise. Mark the wire 15mm and 35mm points from button. Make a loop sticking two points together and twist the loop 6 times counterclockwise.) The bonded specimens were stored at $37^{\circ}C$ saline solution for 3 days. Then the tensile strength of each sample was measured with Instron universal testing machine, crosshead speed of 0.5mm/min. The following results were obtained: 1. As compared to control groups (Group 1) of each material, Rely-a-Bond had a significantly lower mean tensile strengths than other material. (p<0.01) 2. In Group 2. of Ortho-One and Rely-a-Bond, the mean tensile strengths decreased about 7.7% and 11.1%, respectively with statistical significances. (p<0.05) 3. In Group 2. of Ortho-Two and Phase II, the mean tensile strengths did not decrease. 4. In Group 3. of Ortho-One, Rely-a-Bond, Ortho-Two, and Phase II, the mean tensile strengths decreased about 60.8%, 56.1%, 60.2%, and 46.0%, respectively with statistical significances. (p<0.01) 5. In Group 4. of Ortho-One and Rely-a-Bond, the mean tensile strengths did not decrease. 6. In Group 4. of Ortho-Two and Phase II, the mean tensile strengths were decreased about 20.95% and 22.28%, respectively with statistical significances. (p<0.01) There were formations of a hump shaped mass from bonding resin under blood contamination which disturbed direct bonding procedure. According to Reynolds, the proper bond strength for clinical manipulation should be at least 45N or about 4.5Kg.F. According to these results, it can be concluded that Ortho-One could be used during surgical exposure of unerupted teeth. In any case, blood contamination of the etched surface should be avoided, but the blood contamination of primed surface of Ortho-One may not decrease bond strength. Just 'blowing-out' is enough to remove blood from primed surface of Ortho-One. You can verify the clean surface of the primer of Ortho-One after blowing out the blood contamination.

• Journal of Korea Foundry Society
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• v.24 no.1
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• pp.3-9
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• 2004

Die casting is "a process in which molten metal is injected at high velocity and pressure into a mold(die) cavity". Casting with smooth surfaces, high dimensional precision, complicated shapes, and reduced weight can be obtained using this process. But this process is susceptible to casting defects such as porosities, scattered chilled layers, hard spots, etc. For preventing casting defects, we developed "low-velocity high pressure die casting technology", "squeeze die casting technology", "heat insulating sleeve lubricant technology", and "direct pouring technology". The "direct pouring technology" is useful for producing molten metal without oxide contamination. It consists of a pumping system which supplies pure molten metal to the die casting machine. By using this technology, we have successfully reduced oxide contamination in castings to 1/20 of that of our previous castings.

• Journal of Soil and Groundwater Environment
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• v.18 no.1
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• pp.112-122
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• 2013

Current status of soil contamination with fluorine and its source were investigated. The basic principles and procedures of various techniques for the analysis of fluorine contents in soil and solid phase samples were summarized in this review. Analysis of fluorine in solid matrices can be achieved by two types of techniques: (i) UV/Vis spectrophotometer or ion selective electrode (ISE) analysis after performing appropriate extraction steps and (ii) direct solid analysis. As the former cases, the standard method of Korean ministry of environment, alkali fusion-ISE method, pyrohydrolysis, oxygen bomb combustion, aqua regia digestion-automatic analysis, and sequential extraction-ISE method were introduced. In addition, direct analysis methods (i.e., X-ray fluorescence spectrometry and proton induced gamma-ray emission spectrometry) and atomic spectrometry combining with the equipment for introducing solid phase sample were also reviewed. Fluorine analysis techniques can be reasonably selected through site-specific information such as matrix condition, contamination level, the amount of samples and the principles of various methods for the analysis of fluorine presented in this review.

• Journal of Radiation Protection and Research
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• v.15 no.2
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• pp.67-74
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• 1990

A methodology for calculating acceptable levels of contamination of radionuclides in soil for unrestricted use was described. Pathways of exposure include direct radiation from ground surfaces, ingestion of contaminated food and inhalation of resuspended radionuclides. Results calculated using site-specific data for Korean environment were discussed and compared with those estimated by other guidelines.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1590-1595
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• 2003

Direct drive servovalve(DDV) is a kind of one-stage valve since the rotary motion of DC motor is directly transferred to the linear motion of valve spool through the link. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the lead-lag controller is designed using the complex method that is one kind of constrained direct search method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1719-1726
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• 2004

Direct drive servovalve(DDV) is a kind of one-stage valve because the main spool valve is directly driven by the DC motor. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the lead-lag controller is designed using the complex method that is one kind of constrained direct search method.