• Journal of Photoscience
• /
• v.12 no.1
• /
• pp.47-50
• /
• 2005

Mediumeffects have been explored on the competitive H-atom abstraction and SET-promoted, silyl-transfer reactions of excited states of silylalkyl-substituted phenyl ketones. The chemical selectivities of photochemical reactions of silylalkyl phenyl ketones appear to depend on medium polarity, medium silophilicity, added metal cation and alkyl length. Irradiations of silylalkylketones in aqueous solvent system and in presence of metal cation such as $Li^+$ and $Mg^{+2} $lead to formation of acetophenone predominantly by the sequential SET-silyl transfer route.

• Bulletin of the Korean Chemical Society
• /
• v.18 no.12
• /
• pp.1256-1260
• /
• 1997

A series of acyclic polyethers bearing amide end-groups and lipophilic alkyl chains (3-5) were successfully synthesized with quantitative yields. Based upon the transport experiment in a bulk liquid membrane (BLM) system and solvent extraction, a very high selectivity of Pb2+ over other transition metal cations was observed. Measurement of thermodynamic parameters for complexation in methanol at 25 ℃ gave a strong evidence for excellent selective complexation for lead ion over other transition metal ions.

• Korean Journal of Environmental Agriculture
• /
• v.16 no.2
• /
• pp.142-148
• /
• 1997

This study was performed to develop the biological treatment technology of wastewater polluted with heavy metals. Heavy metal-tolerant microorganisms, such as Pseudomonas putida, P. aeruginosa, P. chlororaphis and P. stutzeri possessing the ability to accumulate cadmium, lead, zinc and copper, respectively, were isolated from industrial wastewaters and mine wastewaters polluted with various heavy metals. The effect of competing ions and metabolic inhibitors on heavy metal accumulation in the cells was investigated. Heavy metal accumulation into cells was drastically decreased in the presence of competing cation, $Al^{3+}$, and also decreased, at a lesser extent, in the presence of competing anions, $CO_3\;^{2-}$ and $PO_4\;^{2-}$. But heavy metal accumulation was not influenced generally in the presence of the other rations and anions. The accumulation of Cd, Zn or Cu by Cd-, Zn- or Cu-tolerant microorganism was remarkably decreased in the presence of metabolic inhibitors, but the accumulation of Pb by Pb-tolerant microorganism was little affected in the presence of metabolic inhibitors. These results suggested that the accumulation of Cd, Zn or Cu by Cd-, Zn- or Cu-tolerant microorganism was concerned with the biological activity depending on energy, and the accumulation of Pb by Pb-tolerant microorganism depended on not the biological activity but the physical adsorption on the cell surface. Each heavy metal-tolerant microorganism also exhibited some ability to accumulate the other heavy metals in solution containing equal concentrations of cadmium, lead, zinc and copper, when measured at 48 hours after inoculation of the microorganisms, but the accumulation rates were somewhat low as compared to the accumulation rates of heavy metal fitting to each tolerance. These results suggested that the accumulation of each heavy metal by each heavy metal-tolerant microorganism was a selective accumulation process.

• Journal of Environmental Health Sciences
• /
• v.37 no.5
• /
• pp.348-357
• /
• 2011

Objectives: This study was conducted in order to examine the relationship between heavy metal concentrations in the soil and the level of heavy metals in the blood or urine of 216 local residents living near abandoned metal mines. Methods: Residents around abandoned metal mines were interviewed about their dietary habits, including seafood consumption, medical history, cigarette smoking, and drug history. Metal concentrations in the soil were determined by atomic absorption spectrophotometer (AA-7000, Shimadzu, Japan). Lead (Pb) and cadmium (Cd) contents in the blood or urine were analyzed by GF-AAS (AA-6800, Shimadzu). Mercury (Hg) contents in the blood were determined by means of a mercury analyzer (SP-3DS, NIC). Arsenic (As) content in the soil and urine were measured by a HG-AAS (hydride vapor generation-atomic absorption spectrophotometer). Results: The heavy metal concentrations in the soil showed a log normal distribution and the geometric means of the four villages were 8.61 mg/kg for Pb, 0.19 mg/kg for Cd, 1.81 mg/kg for As and 0.035 mg/kg for Hg. The heavy metal levels of the 216 local residents showed a regular distribution for Pb, Cd, Hg in the blood and As in the urine. The arithmetic means were 3.37 ${\mu}g$/dl for Pb, 3.07 ${\mu}g$/l for Cd and 2.32 ${\mu}g$/l for Hg, 10.41 ${\mu}g$/l for As, respectively. Conclusions: As a result of multi-variate analysis for the affecting factors on the bodily heavy metal concentrations, gender and concentration in the soil (each, p<0.01) for blood lead levels; gender and smoking status (each, p<0.01) for blood cadmium levels; gender (p<0.01) for urine arsenic levels; gender, age and concentration in the soil (p<0.01) for blood mercury levels were shown to be the affecting factors.

• Journal of the Korean Society of Radiology
• /
• v.12 no.2
• /
• pp.173-178
• /
• 2018

Lead is a very useful material in shielding radiation in hospitals. But lead is toxic. Therefore, there are many studies on substitutable materials, Typically, there are many studies using tungsten. In this study, we investigated the physical properties of lead and tungsten and the Half value layer. As a result, lead having higher atomic number showed higher cross - sectional area than tungsten. But, at the same size, the electron density of tungsten with a high density is about 1.7 times higher than that of lead. In MCNPX simulation, the shielding effect of tungsten is about 1.4 times higher than that of lead, It was confirmed that tungsten had better shielding efficiency than lead. However, considering the economic aspect, tungsten is a rare metal, which is about 25 times more expensive than lead, which is considered to be inappropriate as an alternative to lead.

• Journal of Environmental Science International
• /
• v.13 no.1
• /
• pp.61-68
• /
• 2004

Three kinds of toxic heavy metals, such as lead, copper, and cadmium, existing abundantly in contaminated soils were selected to investigate pH change, electroosmotic flow, and the removal rate in the application of electrokinetic process. In the change of pHs, they reached to about 12 and 2 at each cathodic and anodic region, respectively, and maintained for reaction being proceeded. Electroosmotic flow rates were not influenced by the kind of metal species but by electropotential gradient. On the soils contaminated by each metal, the removal rate of Cd was the fastest among three as in the order of Cd>Pb>Cu. While on the soils contaminated by mixed metal species, Cu was the fastest. Metal species transported by electrokinetic processes were distributed in between 0.9 and 1.0 of normalized region. In the case of soils contaminated by one kind of metal. the relative concentrations of Pb and Cd estimated in between normalized region 0.9 and 1.0 were 5.2 and 5.7, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.1 s.256
• /
• pp.11-17
• /
• 2007

In this paper, we present a design, analysis, fabrication and performance test of the novel DoD metal-jet system for application to the high-density and high-temperature-melting materials. The theoretical analysis of the metal-jet nozzle system is derived by using electro-mechanical analogy. Based on the theoretical analysis results, we design the metal-jet print head system and fabricate the metal-jet system, which can eject the droplet of lead-free metal solder in high-temperature. In the experimental test, we set up the test apparatus for visualization of the droplet ejection and measure the ejected droplet volume and velocity. As a result, the diameter, volume and the velocity of the ejected droplet are about 65 $\mu$m $\sim$ 70 $\mu$m, 145p1 $\sim$ 180 pl and 4m/s, which shows quite good agreement with the theoretical analysis results of the 75 $\mu$m-diameter and 220 pl-volume of droplet. In comparison with the experimental result, the errors of diameter and volume are 7% $\sim$ 13% and 18 $\sim$ 34%, respectively.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.82.2-82.2
• /
• 2010

The development of bipolar plate having high efficiency and chemical properties has a major impact on fuel cell applications commercialization. Even though graphite bipolar plate has high electric conductivity and chemical resistance, it has demerits about mass production and brittle property for commercialization. Hence, metallic bipolar plate can be substitute for fuel cell bipolar plate. Although its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions, metallic bipolar plate for PEMFC is more suitable for automotive and residential power generation system because of its high mechanical strength, low gas permeability and applicability to mass production. Therefore, several types of coating has been applied to prevent corrosion and oxide film growth and to achieve more high durability. This work presents durability of coated metal bipolar plate for low temperature PEMFC which made for fuel cell vehicle. This results showed surface treatment increase long-term durability, even electric conductivity and corrosion resistance.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.15 no.1
• /
• pp.95-102
• /
• 2016

Wrinkle, spring-back, and fracture are major defects frequently found in the sheet metal forming process, and the reduction of such defects is difficult as they are affected by uncontrollable factors, such as variations in properties of the incoming material and process parameters. Without any countermeasures against these issues, attempts to reduce defects through optimal design methods often lead to failure. In this research, a new multi-attribute robust design methodology, based on the Mahalanobis Taguchi System (MTS), is presented for reducing the possibilities of wrinkle, spring-back, and fracture. MTS performs experimentation, based on the orthogonal array under various noise conditions, uses the SN ratio of the Mahalanobis distance as a performance metric. The proposed method is illustrated through a robust design of the sheet metal forming process of a cross member of automotive body.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2008.05a
• /
• pp.827-831
• /
• 2008

In this study, the effects of reclaimed wastewater irrigation on the concentration of heavy metals such as lead, zinc, cadmium, and copper in soil and vegetables were investigated by monitoring an experimental area irrigated with reclaimed wastewater. Three treatments and three replications on $10{\times}2$-m plots were installed and heavy metal concentrations in soil and vegetables were monitored from 2005 to 2007. The treatments applied in this study were groundwater irrigation (control treatment), wastewater irrigation, and irrigation with filtered reclaimed wastewater treated with ultraviolet light. The monitored results showed that the concentrations of Cu, Cd, and Pb in soil during the experimental period were lower than initial soil levels before irrigation, whereas Zn increased in all treatment plots. However, the ranges of Zn, Cu, Cd and Pb in soil were below the soil pollution standards in the Republic of Korea. Heavy metal concentrations in vegetables showed insignificant variations for all treatments.