• 상하수도학회지
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• 제28권3호
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• pp.287-297
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• 2014

It is important to predict chlorine decay with different water purification processes and distribution pipeline materials, especially because chlorine decay is in direct relationship with the stability of water quality. The degree of chlorine decay may affect the water quality at the end of the pipeline: it may produce disinfection by-products or cause unpleasant odor and taste. Sand filtrate and dual media filtrate were used as influents in this study, and cast iron (CI), polyvinyl chloride (PVC), and stainless steel (SS) were used as pipeline materials. The results were analyzed via chlorine decay models by comparing the experimental and model parameters. The models were then used to estimate rechlorination time and chlorine decay time. The results indicated that water quality (e.g. organic matter and alkalinity) and pipeline materials were important factors influencing bulk decay and sand filtrate exhibited greater chlorine decay than dual media filtrate. The two-component second-order model was more applicable than the first decay model, and it enabled the estimation of chlorine decay time. These results are expected to provide the basis for modeling chlorine decay of different water purification processes and pipeline materials.

• 분석과학
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• 제23권4호
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• pp.395-404
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• 2010

레몬과 콩 그리고 채소류에서 105개의 잔류농약을 다종 다성분 분석법으로 GC/MS/MS 분석하였다. 각 시료로부터 acetonitrile로 1차 추출하고 NaCl 15 g을 첨가한 다음 액-액 분배하였으며, Florisil 고체상(SPE) Cartridge로 정제하여 분석하였다. 레몬과 콩에서의 105개 농약의 회수율은 azinphos-methyl, famoxadone, fenamidone, flufenoxuron, triadimefon을 제외한 모든 농약에서 우수한 것으로 나타났는데 레몬에서 71.1~126.0%, 콩에서는 72.5~124.5% 였다. 또한 레몬에서의 검출한계와 정량한계는 각각 0.001~150 ng/mL와 0.004~500 ng/mL으로 확인되었다.

• 대한두경부종양학회지
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• 제11권2호
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• pp.153-157
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• 1995

The effects of radiation therapy on salivary function of parotid gland were studied 20 male patients by radiation for tumors of head and neck. Saliva samples were collected before, during the radiotherapy and follow up. Parotid salivary function was quantitatively evaluated using a sialometry, sialochemistry, and scintigraphy. Salivary flow rates decreased in all individuals after irradiation. Glands than were partially irradiated were more likely to have some residual function than fully irradiated glands. Sodium and chloride contents were increased in parotid saliva of radiation patients where as potassium content was not changed definitively, pH was not changed during radiotherapy, but increased during follow up period. Scintigraphic stimulatory response rates showed similar result as flow rates. These results showed that exclusion of partial parotid gland from radiation is necessary to prevent severe xerostomia.

• 조명전기설비학회논문지
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• 제25권1호
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• pp.85-92
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• 2011

The role of RCDs(Residual Current Protective Device) that are installed before the load is very important for preventing electric shock and electrical fire. However, although fault rate of RCD is increasing due to deterioration and long period usage, the RCD is permanently used without a checking of performance evaluation and it causes the electrical accident. In this paper, the amount of airborne chloride is researched in domestic costal area and the accelerated life test is conducted using a salt water spray tester in order to decide the life time of RCD. Aa a result of an accelerated life test, the MTTF(Mean Time To Failure) of RCD is 110.81 hours and B10 life time of RCD is 45.81 hours for the all samples. when an accelerated life test result is applied to within 2 km costal area, the life time of RCD is predicted about 5 years.

• Journal of Microbiology and Biotechnology
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• 제16권7호
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• pp.1060-1067
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• 2006

This study was undertaken to determine the effect of reservoirs on water quality and the distribution of pathogenic and indicator bacteria in a drinking water distribution system (total length 14km). Raw water, disinfected water, and water samples from the distribution system were subjected to physicochemical and microbiological analyses. Most factors encountered at each season included residual chloride, nitrate, turbidity, and phosphorus for heterotrophic bacterial distribution, and hardness, heterotrophic bacteria, sampling site, and DOC (dissolved organic carbon) for bacteria on selective media. No Salmonella or Shigella spp. were detected, but many colonies of opportunistic pathogens were found. Comparing tap water samples taken at similar distances from the water treatment plant, samples that had passed through a reservoir had a higher concentration of heterotrophic bacteria, and a higher rate of colony formation with 10 times as many bacteria on selective media. Based on the results with m-Endo agar, the water in reservoirs appeared safe; however, coliforms and opportunistic pathogenic bacteria such as Pseudomonas aeruginosa were identified on other selective media. This study illustrates that storage reservoirs in the drinking water distribution system have low microbiological water quality by opportunistic pathogens, and therefore, water quality must be controlled.

• 한국분말재료학회지
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• 제16권2호
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• pp.98-103
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• 2009

The ultrafine titanium carbonitride particles ($TiC_{0.7}N_{0.3}$) below 100nm in mean size were successfully synthesized by Mg-thermal reduction process. The nanostructured sub-stoichiometric titanium carbide ($TiC_{0.7}$) particles were produced by the magnesium reduction at 1123K of gaseous $TiC_{l4}+xC_2Cl_4$ and the heat treatments in vacuum were performed for five hours to remove residual magnesium and magnesium chloride mixed with $TiC_{0.7}$. And final $TiC_{0.7}N_{0.3}$ phase was obtained by nitrification under normal $N_2$ gas at 1373K for 2 hrs. The purity of produced $TiC_{0.7}N_{0.3}$ particles was above 99.3% and the oxygen contents below 0.2 wt%. We investigated in particular the effects of the temperatures in vacuum treatment on the particle refinement of final product.

• 한국분말재료학회지
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• 제11권4호
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• pp.322-327
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• 2004

Ultrafine titanium carbide particles were synthesized by the reaction of liquid-magnesium and vaporized TiCl$_{4}$+C$_{x}$Cl$_{4}$(x = 1 and 2) solution. Fine titanium carbide particles with about 50 nm were successfully produced by combining Ti and C atoms released by chloride reduction of magnesium, and vacuum was then used to remove the residual phases of MgCl$_{2}$ and excess Mg. Small amounts of impurities such as O, Fe, Mg and Cl were detected in the product, but such problem can be solved by more precise process control. The lattice parameter of the product was 0.43267 nm, near the standard value. With respect to the reaction kinetics, the activation energy for the reactions of TiCl$_{4}$+C$_{2}$Cl$_{4}$and Mg was found to 69 kJ/mole, which was about half value against the use of TiCl$_{4}$+CCl$_{4}$, and such higher reactivity of the former contributed to increase the stoichiometry until the level of TiC$_{0.96}$ and decrease the free carbon content below 0.3 wt.%.

• Journal of Welding and Joining
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• 제14권2호
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• pp.36-45
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• 1996

Fatigue strength of the spot welded lap joint is considerably influenced by corrosive environments. Particularly, the chloride and the sulfide are most injurious to strength of the spot welded lap joint. Therefore, there is a need to evaluate its effect to corrosion fatigue strength for safe life design of spot welded structures. In order to evaluate their corrosion fatigue strength, corrosion fatigue tests on the spot welded lap joints of the uncoated and the coated high strength steel sheets were conducted in air and in 10% NaCl solution. Corrosion fatigue strength of the uncoated specimens were entirely lower than the coated one in NaCl solution, but those of the coated specimens in NaCl solution were lower than in air. And stress distribution in single spon welded lap joint subjected to tension-shear load was investigated by the finite element method. Using these results, we tried to evaluate corrosion fatgue strength of the various spot welded lap joints with maximum stress $\sigma_{max}$ at edge on loading side of the spot welded lap joint. We could find that corrosion fatigue strength could be quantitatively and systematically rearranged by $\sigma_{max}$.

• 폴리머
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• 제24권6호
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• pp.757-762
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• 2000

4-히드록시스티릴피리딘과 4-비닐벤질클로리드를 반응시켜 감광성 단량체로서 비닐벤질옥 시스티릴피리딘 (VSP)을 합성하였다. 5-20 mo1%의 VSP를 로진 moiety를 함유하는 메타크릴단량체와 라디칼 공중합하여 로진 moiety를 함유하는 몇가지 광경화성 고분자를 합성하였다. UV분광법으로 결정한 공중합체 중의 VSP의 함량은 5.3-17.3mol%정도였다. 이들 고분자의 수평균 분자량은 18000-28000정도였고 다분산지수는 1.8 정도였으며, 또한 유리전이온도는 15$0^{\circ}C$ 부근이였고 초기 열분해온도는 34$0^{\circ}C$ 정도였다. 이들 고분자는 자외선에 의해 비교적 빠르게 경화되었고, 이 광경화 반응은 UV분광법과 잔막수율법으로 분석될 수 있었다.

• 생태와환경
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• 제43권4호
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• pp.453-458
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• 2010

DOC (Dissolved Organic Carbon) is an operational terminology for organic carbon molecules dissolved in natural waters. DOC has been studied by ecologists extensively, because it plays a key role in various ecological functions such as substrates for secondary production and the carbon cycle. DOC also represents a substrate for microbial growth within potable water distribution systems, and can react with disinfectants (e.g., chloride) to form harmful disinfection by-products. In addition, residual DOC may carry with it organically bound toxic heavy metals. DOC in aquatic ecosystems may ultimately be transported to the oceans, or released back to the atmosphere by heterotrophic respiration, which can accelerate global climate change. There is evidence that DOC concentrations in aquatic ecosystems are increasing in many regions of the world including Europe, North America, and even in Korea. Land use changes, elevated temperature, elevated $CO_2$, recovery from acidification, and nitrogen deposition have been proposed as mechanisms for the trend. However, the key driving mechanism is yet to be conclusively determined. We propose that more extensive and longer-term observations, research of chemical properties of DOC, impacts of elevated DOC on environmental issues and interdisciplinary approaches are warranted as future studies to fill the gaps in our knowledge about DOC dynamics.