• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.313-319
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• 1999

The development of deformation texture in FCC polycystalline metals during rolling was simulated by the finite element analysis using a large-deformation, elaatic-plastic, rate-dependent polycrystalline model of crystal plasticity. Different plastic anisotropy due to different orientation of each crystal makes inhomogeneous deformation. Assuming plane strain compression condition, the simulation with a high rate sensitivity resulted in main component change from Dillamore at low rate sensitivity to Brass component.

• Environmental Analysis Health and Toxicology
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• v.25 no.1
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• pp.19-26
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• 2010

Discharged materials from the point or non-point source are released into the sea, and as the results, marine environment is directly affected. We must estimate the impacts of contaminants to marine pollution rapidly and accurately. Therefore, it is needed on early warning system for appreciating marine environmental impacts, and required a bioassay to evaluate abnormal changes. A bioassay test was developed to examine the effects of heavy metal contaminants on the early life stages of the marine annimals. We have studied the effects of metals on early development of a sea urchin species, Strongylocentrotus intermedius. S. intermedius embryos were tested with six metals (Cu, Ag, Zn, Cd, Cr, Ni) and showed the highest sensitivity to Cu as well as the lowest sensitivity to Cd. The order of biological impact for metals was Cu>Ag>Ni>Zn>Cr>Cd. In accordance with the results, sea urchins embryos can provide biological criteria for seawater quality assessment. The sensitivity of developmental bioassay whith S. intermedius is at intermediate level among marine organisms commonly used in aquatic bioassays. And this sea urchin can be routinely employed as a test organism for ecotoxicity assays.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.06a
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• pp.11-23
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• 1994

Formability of sheet metals can be evaluated using tensile testing. Easily measured tensile properties such as yield strength, tensile strength, elongation, strain hardening exponent, strain rate sensitivity and plastic strain ratio are important parameters to evaluated the sheet formability. This paper briefly explains how these properties are related to deep drawability and stretchability. The plastic anisotropy of sheet metals is usually attributed to the crystallographic texture. However dislocation distribution may influence the anisotropy.

• Journal of Powder Materials
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• v.19 no.4
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• pp.297-303
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• 2012

In this study, voltammetry system for realizing high sensitivity nano-labeled sensor of detecting heavy metals was designed, and optimal system operating conditions were determined. High precision digital to analog converter (DAC) circuit was designed to control applied unit voltage at working electrode and analog to digital converter (ADC) circuit was designed to measure the current range of $0.1{\sim}1000{\mu}A$ at counter electrode. Main control unit (MCU) circuit for controlling voltammetry system with 150 MHz clock speed, main memory circuit for the mathematical operation processing of the measured current value and independent power circuit for analog/digital circuit parts to reduce various noise were designed. From result of voltammetry system operation, oxidation current peaks which are proportional to the concentrations of Zn, Cd and Pb ions were found at each oxidation potential with high precision.

• Journal of environmental and Sanitary engineering
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• v.10 no.2
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• pp.46-58
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• 1995

Acute toxicity of heavy metals( Mercury, Cadmium, Lead, Chromium and Copper ), Organophosphorus insecticides( EPN, 2, 4- D, and Parathion ), and other chemicals( Arsenic, Cyanide, and Phenol) to Daphnia magna, and Vibrio fischeri was analysed. Daphnia magna to most toxic chemicals was most sensitive among test organisms alld then Daphnia magna seems to be more useful in toxic test of water. Daphnia magna was more sensitive to heavy metals than insecticides and other chemicals. The sensitivity of Visrio JircAeri to heavy metals was not so different from that to insecticides and the sensitivity to other chemicals was low. Visrio JircAeri appears to be more sensitive to toxic chemicals than Photobacterium phosphoreum, which was compared as recorded values of P.phosphoreum. Toxic chemicals were classified as Group 1 which had a high $EC_{50}$ or $LC_{50}$ value and the low increase rate of toxicity according to the increase of concentration, Group 2 which had a high $EC_{50}$ or $LC_{50}$ value and the high increase rate of toxicity, Group 3 which had a low $EC_{50}$ or $LC_{50}$ value and the high increase rate of toxicity, and Group 4 which had a low $EC_{50}$ or $LC_{50}$ value and the low increase rate of toxicity. To Daphnia magna, Lead, Chromium EPN, and Parathion were included in Group 1 : Mercury and Copper in Group 2 : Arsonic and Cadmium in Group 3 : Cyanide, 2, 4-B, and Phenol in Group 4. To Visrio JircAeri, Lead, Chromiurl 2, 4- D, and Parathion were included in Group 1 : Merecury, Cadmium and Arsenic in Group 2 : Cyanide in Group 3 : EPN, Copper, and Phenol in Group 4.

• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.1-8
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• 2011

To measure the sensitivity of the hydrogen embrittlement from plated high strength bolts (SWCH18A, F11T), the bolt was stressed by a corresponding to the amount of tensile strain of 5% and 20%, and then the bolt developed a crack on the surface. The bolt that didn't have concentrated hydrogen, even though it was stressed by a corresponding the amount of tensile strain of 5% and 20%, no crack developed. However, the bolt that had concentrated hydrogen, developed cracks from the thread crest to the root. It is impossible to measure the hydrogen amount from plated high strength bolts using Hydrogen-Determinator, because of the limitation of the minimum sample size (about 1g as a mass or $5{\times}5{\times}5 mm^3$ as a volume). Therefore, the sensitivity of hydrogen embrittlement can be measured by observing the presence of cracks on the surface of plated high strength bolts which are stressed by a corresponding to the amount of tensile strain of 5% and 20%.

• Korean Journal of Metals and Materials
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• v.48 no.4
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• pp.342-346
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• 2010

Pd nanoparticles (NPs) were successfully functionalizedon the surfaces of single-walled carbon nanotubes (SWNTs) by dendrimer-mediated synthesis. The hydrogen sensing properties of the Pd NPs functionalized SWNTs were investigated. Pd NPs-dendrimer-SWNTs sensors show much better speedsand superior recovery rates but lower sensitivity compared to Pd NPs-functionalized SWNTs directly fabricated due to the existence of dendrimers. Pyrolysis of the dendrimers by heat treatment resulted in a fast response time and high sensitivity owing to the reduced length of the dendrimers. These results demonstrate that the heat treatment of dendrimers in Pd NPs-dendrimer-SWNTs sensors can enable significant electrical conductance modulation upon exposure to extremely low concentrations (10 ppm) of hydrogen gas ($H_2$) in air.

• The Korean Journal of Malacology
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• v.22 no.2
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• pp.167-173
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• 2006

The embryos of marine bivalves have been commonly used in bioassays for quality assessments of marine environments. Although several standard protocols for the developmental bioassay of bivalves have been proposed, only a few trials for application of these protocols in environmental assessments or for the development of a new protocol with Korean species have been conducted. As such, there is a strong need to establish standard bioassay protocols with bivalves commonly found in Korean waters. To determine the sensitivity of Mytilus galloprovincialis to establish a standard bioassay, their fertilized eggs were exposed to six metals (Ag, Cd, Cr, Cu, Ni, and Zn). The order of biological impact was Ag > Cu > Ni > Zn > Cr > Cd and their lowest observed effective concentration were 5, 16.4, 25.4, 142, 187 and 1,500${\mu}g/l$, respectively. The proportion of normal larvae appeared to decrease linearly with the logarithm of each toxicant concentration within the tested range. The average values of median effective concentrations $(EC_{50})$ from the triplicate experiments for Ag, Cd, Cr, Cu, Ni, and Zn were 6.8, 1,797, 786, 16.6, 68.1, and 139.2${\mu}g/l$, respectively. There was a more than 100-fold difference in $EC_{50}$ values of Cu and Cd. The value of $EC_{50}$ or median lethal concentration of Cu was within the range observed for other bivalve developmental bioassays. The overall sensitivity of M. galloprovincialis in the present developmental bioassay was also similar to that of other marine organisms commonly used in aquatic bioassays (e.g. sea urchins, oysters). Hence, the bioassay using the embryo of M. galloprovincialis is considered to be a useful tool to monitor and evaluate the quality of marine aquatic environments.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.1
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• pp.146-159
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• 2011

The continuous increase in the production of metals and their subsequent release into the environment has lead to increased concentration of these elements in agricultural soils. Because microbes are involved in almost every chemical transformations taking place in the soil, considerable attention has been given to assessing their responses to metal contaminants. Short-term and long-term exposures to toxic metals have been shown to reduce microbial diversity, biomass and activities in the soil. Several studies show that microbial parameters like basal respiration, metabolic quotient, and enzymatic activities, including those of oxidoreductases and those involved in the cycle of C, N, P and other elements, exhibit sensitivity to soil metal concentrations. These have been therefore, regarded as good indices for assessing the impact of metal contaminants to the soil. Metal contamination has also been extensively shown to decrease species diversity and cause shifts in microbial community structure. Biochemical and molecular techniques that are currently being employed to detect these changes are continuously challenged by several limiting factors, although showing some degree of sensitivity and efficiency. Variations and inconsistencies in the responses of bioindicators to metal stress in the soil can also be explained by differences in bioavailability of the metal to the microorganisms. This, in turn, is influenced by soil characteristics such as CEC, pH, soil particles and other factors. Therefore, aside from selecting the appropriate techniques to better understand microbial responses to metals, it is also important to understand the prevalent environmental conditions that interplay to bring about observed changes in any given soil parameter.

• Proceedings of the Korean Society of Toxicology Conference
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• 2002.11b
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• pp.174-174
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• 2002

Metallothioneins (MTs) are known to be induced by heavy metals in various organs of different species and represent a potential biomarker of aquatic contamination by heavy metals. In this work, cloning and sequencing of a metallothionein gene in crucian carp (Carassius auratus) was done and sensitivities and specificities of the gene expressions were compared.(omitted)