• Korean Journal of Environmental Biology
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• v.23 no.2 s.58
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• pp.98-105
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• 2005

The relative sensitivity of two freshwater non- biting midges, Chironomus yoshimatsui Martin and Sublette and C. riparius Meigan, was examined for lead, cadmium, and mercury in water- only exposures. Two endpoints were compared to assess toxicity 48 h and 96 h after exposure: Acute toxicity ($50\%$ lethal concentration: $LC_50$) and behavioral toxicity ($50\%$ effective concentration: $EC_{50}$). for the behavioral toxicity, reduction of swimming performance of two midge species in the treated conditions was compared to that in the untreated control. The sensitivities differed depending on the species and heavy metals, although some trends emerged. $LC_50$ values in C. yoshimatsui to cadmium and lead were always higher than those in C. riparius with increasing toxicity, regardless of the exposure times. The opposit was true for the mercury treatment. Similar trends were observed in the $EC_{50}$ values. The $EC_{50}$ values were always lower than the $LC_50$ values in all the treatment cases (midge species, heavy metals, and exposure times). These results indicate that the two midge species respond to the heavy metals differently: C. riparius is sensive to cadmium and lead and C. yoshimatsui to mercury. Behavioral toxicity such as swimming performance can be an effective endpoint for assessing heavy metal toxicity in water.

• Journal of Sensor Science and Technology
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• v.6 no.4
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• pp.274-279
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• 1997

NOx sensors using tungsten oxide films as a base material were prepared and their electrical and sensing characteristics have been investigated. The $WO_{3}$ thick films doped with $SnO_{2}$ or $TiO_{2}$ showed higher sensitivity and better sorption characteristics to NOx gas than the pure $WO_{3}$ films material in air at operating temperature of $400^{\circ}C$. By addition of noble catalysts, such as Ru or Au, to the $TiO_{2}-WO_{3}$ thick films, their sensitivity, recovery and selectivity to NOx gas were found to be more enhanced.

• Journal of the Korean Society of Urban Environment
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• v.18 no.4
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• pp.429-437
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• 2018

In this study, the mixed toxicity of heavy metals (Cu, Pb, Hg) and surfactants (SLS, ALS) was evaluated by using Vibrio fischeri and Daphnia magna. The sensitivity of ecotoxicity to heavy metals was sensitive to daphnia but the case of surfactants were more sensitive to Vibrio fischeri. Experimental results of Vibrio fischeri show that the toxicity value P(O) was lower than the predicted value P(E), and the antagonistic effect was observed when the heavy metal and the surfactant were mixed. It seems that SLS and ALS, which are anionic surfactants, have anionic form on the hydrophilic head, so that they have an antagonistic effect that they are bonded with heavy metal ion which is a cation type and the actual toxicity is lowered. In Daphnia magna, the results showed that antagonistic, additive and synergistic effects were in order as concentrations increased. As the concentration increases, Daphnia magna, which is highly sensitive to heavy metals, seems to have a synergistic effect with a rapid increase in mortality.

• Journal of Environmental Health Sciences
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• v.26 no.4
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• pp.65-74
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• 2000

The sensitivity of a mehtanogen and sulfate-reducing bacterium isolated from a sea-based landfill site Cd$^{2+}$ and CU$^{2+}$ was studied. Methanogens and sulfate-reducing bacteria in leachates of the waste disposal site were enumerated using the MPN method. Methanobacterium thermoautotrophicum KHT, isolated from the leachate, could not grow at 0.5 mM Cd$^{2+}$ or 1.0 mM CU$^{2+}$. Desulfotomaculum sp. RHT, isolated from the same leachate, was able to insolubilization 3.0 mM Cd$^{2+}$ or 2.0 mM CU$^{2+}$ by production of hydrogen sulfide. When strains KHT and RHT were cultured together in the presence of the heavy metals, strain KHT could grow at high heavy metal concentrations after insolubilization of the metals by strain RHT. strain RHT.

• Particle and aerosol research
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• v.10 no.2
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• pp.53-59
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• 2014

Palladium (Pd) nanoparticles attached graphene (GR) composite was synthesized for an enhanced glucose biosensor. Aerosol spray pyrolysis (ASP) was employed to synthesize the GR-Pd composite using a colloidal mixture of graphene oxide (GO) and palladium chloride ($PdCl_2$) precursor. The effects of the weight ratio of the Pd/GR on the particle properties including the morphology and crystal structure were investigated. The morphology of GR-Pd composites was generally the shape of a crumpled paper ball, and the average composite size was about $1{\mu}m$. Pd nanoparticles less than 20 nm in diameter were deposited on GR sheets and the Pd nanoparticles showed clear crystallinity. The characteristic of the glucose biosensor fabricated with the as-prepared GR-Pd composite was tested through cyclic voltammetry measurements. The biosensor exhibited a high current flow as well as clear redox peaks, which resulted in a superior ability of the catalyst in terms of an electrochemical reaction. The highest sensitivity obtained from the amperometric response of the glucose biosensor was $14.4{\mu}A/mM{\cdot}cm^2$.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.1
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• pp.93-100
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• 2012

In this paper, the deterministic optimal design for the tail plane made of composite materials is conducted under the deterministic loading condition and compared with that of the metallic materials. Next, the reliability analysis with five random variables such as loading and material properties of unidirectional prepreg is conducted to examine the probability of failure for the deterministic optimal design results. The MATLAB programing is used for reliability analysis combined with FEA S/W(COMSOL) for structural analysis. The laminated composite is assumed to the equivalent orthotropic material using classical laminated plate theory. The response surface methodology and importance sampling technique are adopted to reduce computational cost with satisfying the accuracy in reliability analysis. As a result, structural weight of composite materials is lighter than that of metals in deterministic optimal design. However, the probability of failure for the deterministic optimal design of the tail plane structures is too high to be neglected. The sensitivity of each variable is also estimated using probabilistic sensitivity analysis to figure out which variables are sensitive to failure. The computational cost is considerably reduced when response surface methodology and importance sampling technique are used. The study of the computationally inexpensive method for reliability-based design optimization will be necessary in further work.

• Journal of Environmental Health Sciences
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• v.18 no.2
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• pp.135-145
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• 1992

This study was carried out to find out some characteristic responses of biological samples under the exposure of trace metals with the considering of Sex, age, residence period and smoking. Blood, Urine and Hair were collected from 116 dwellers in the vicinity of a smelting factory. Cd, Cu, Pb and Zn concentrations were determined by flame atomic absorption spectrophotometry and the following results were found important. 1) The concentrations of trace metals in the blood were 0.010+ 0.003 $\mu$g/ml in Cd, 0.82+ 0.11 $\mu$g/ml in Cu, 0.23_+ 0.13 $\mu$g/ml in Pb and 5.78_+ 1.43 $\mu$g/ml in Zn, those in the urine were 1.7_+ 1.7 $\mu$g/l in Cd, 16.5_+ 16.0 $\mu$g/l in Cu, 24.6_+ 23.0 $\mu$g/l in Pb and 367.7_+ 283.4 $\mu$g/l in Zn, and those in the hair were 0.52_+ 0.56 $\mu$g/g in Cd, 11.00_+4.01 $\mu$g/g in Cu, 8.53_+ 7.05 $\mu$g/g in Pb and 383.23_+ 110.56 $\mu$g/g in Zn. 2) In sex, the concentrations of Zn in the blood and urine of male were higher than those of female, however, the concentrations of Cd and Zn in the hair of female were higher than those of male. 3) The concentrations of Cd, Pb and Zn in the urine showed an increasing trend by age. 4) While the concentration of Cd in the urine increased, the concentration of Pb in the hair decreased by residential period in all the samples. 5) The concentrations of Cd and Zn in the blood and that of Zn in the urine of smoking group were higher than those of non-smoking group. The concentration of Pb in the blood of smoking group and those of Cd, Pb and Zn in the urine of non-smoking group showed increasing the trend by age. The concentrations of Cd and Zn in the urine of non-smoking group, the concentration of Zn in the hair of smoking group showed increasing trend by residential period, however, the concentrations of Pb in the blood and hair and that of Zn in the hair showed decreasing trend by residential period. 6) When the correlations of the concentrations between Zn (main smelting metal) and other metals were analyzed, Zn in the blood was significantly correlated with Cu, Pb and Zn in the urine (positively) and Zn in the urine was significantly correlated with Zn in the blood, Cd, Cu and Pb in the urine, and Pb in the hair (positively). Zn in the hair was significantly correlated with Cd in the urine and Cu in the hair (positively). 7) Consequently, it was useful to note that samples of urine showed higher sensitivity under the metal exposure than those of blood and hair in individual sampling. In addition, as trace metals showed higher accumulation in the hair of the groups, sampling of hair was more highly recommended than those of urine and blood in group sampling.

• Ocean and Polar Research
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• v.26 no.2
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• pp.187-197
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• 2004

The purpose of this paper is to investigate economic feasibility of manganese nodules in Korea area (Clarion-Clipperton Fracture Zone). We assumed that the production scale of manganese nodules were 3.0MT or 1.5MT and analyzed that the capital cost and operating cost were estimated in the four sectors, exploration, mining, transportation and metallurgical process. The capital cost and operating cost evaluation reflects the latest technical practices. First, for analyzing economic feasibility, the scenario suggests that the production of 4 metals can be made for 25 years. Assuming the discount rate at 8.0%, equity capital at 50% and tax at 27%. When manganese nodule were mininged 3.0 MT, economic feasibility analyses showed that IRR was 12.8 and pay-back period was 9.2 years, and when manganese nodules were mininged 1.5 MT, economic feasibility analyses showed that IRR was 4.0 and pay-back period was 11.8 years. This study indicated there is economic validity of at the product of manganese nodules 3.0 MT. In addition, we carried out a sensitivity analysis at the change of cobalt price on mining 1.5 MT. The result of sensitivity analysis clearly showed that economic validity is high at increasing of cobalt price 50% up.

• International Journal of Automotive Technology
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• v.6 no.4
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• pp.413-419
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• 2005

The United States automotive recycling infrastructure has successfully reduced the amount of automotive waste sent to landfills, especially since the introduction of shredders in the late 1950s. Shredders are necessary to process and recycle automotive hulks and other durable goods. However, this industry faces significant challenges as the automotive manufacturers are increasing the use of nonmetallic components which are difficult to recycle. Additionally, it is becoming obvious that automobiles contain hazardous materials which place heavy burdens on the environment. To address this growing concern, we propose a process planning model for automotive shredders to make tactical decisions regarding at what level to process and at what level to reprocess feed stock materials. The purpose of this paper is to test analytical models to help shredders improve the profitability and efficiency of the bulk recycling processes for end of life automobile returns. The work is motivated by an actual recycling problem that was observed at Capitol City Metals shredding facility in Indianapolis, Indiana.

• Progress in Superconductivity and Cryogenics
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• v.21 no.3
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• pp.22-26
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• 2019

With an increasing potential to realize quantum computer, it has recently been an important issue to extend the capabilities of RF cavities to maintain longer coherent quantum system. Using superconductors instead of normal metals allows the quantum system to have a substantially enhanced quality factor. In this paper, surface impedances of superconducting cavities are calculated by the Mattis-Bardeen theory with Python & MATLAB programs. With a simulation of electromagnetic field distribution, the sensitivity to dielectric and surface losses of the superconducting cavities are determined. Then calculations of the resonance frequency and quality factor of three-dimensional superconducting resonators made of Al or Nb are discussed.