• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.11
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• pp.683-689
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• 2015

For the formation of $N^+$ doping, the antimony ions are mainly used for the fabrication of a BJT (bipolar junction transistor), CMOS (complementary metal oxide semiconductor), FET (field effect transistor) and BiCMOS (bipolar and complementary metal oxide semiconductor) process integration. Antimony is a heavy element and has relatively a low diffusion coefficient in silicon. Therefore, antimony is preferred as a candidate of ultra shallow junction for n type doping instead of arsenic implantation. Three-dimensional (3D) profiles of antimony are also compared one another from different tilt angles and incident energies under same dimensional conditions. The diffusion effect of antimony showed ORD (oxygen retarded diffusion) after thermal oxidation process. The interfacial effect of a $SiO_2/Si$ is influenced antimony diffusion and showed segregation effects during the oxidation process. The surface sputtering effect of antimony must be considered due to its heavy mass in the case of low energy and high dose conditions. The range of antimony implanted in amorphous and crystalline silicon are compared each other and its data and profiles also showed and explained after thermal annealing under inert $N_2$ gas and dry oxidation.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.4
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• pp.11-17
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• 2009

Polarography is a subclass of voltammetry where the working electrode is a dropping mercury electrode. More, I developed the experiment for raising up mercury electrode. In Voltammetry, information about an analyte is obtained by measuring the current as the potential is varied at oxidation-reduction reaction. A plot of current vs. potential in a polarography experiment shows the current oscillations correspoding to the drops of Hg falling from the capillary. The drops growth causes capacitive and faradic current. These changing current effects combined with experiments where the potential is continuously changed can result in noisy traces. The raising up type improved upon the method of dropping in hardware. In reduction of the noise, moving average smoothing method have been used. But the other procedure is introduced based on Fourier transformation. So FFT and IFFT engine was implemented and installed in my experiment. However, after experimentation, peak height as the measuring parameter gave a good linear relationship to concentration. The resolution of potential peaks of various kinds, using Zn and Cu as the example, was improved using the smoothing method.

• Asian Journal of Atmospheric Environment
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• v.7 no.1
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• pp.56-63
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• 2013

Children are particularly vulnerable to adverse health effects associated with heavy metal exposure. The goal of this study was to investigate the relationship between proximity to an industry complex and blood lead and urinary cadmium levels for children aged 7-13 who lived in Ulsan where a big petrochemical complex is located. We conducted a questionnaire survey to collect data including sociodemographics, daily habits, residential environment, etc. We also analyzed blood lead and urinary cadmium levels using Atomic Absorption Spectrometry (AAS). Data were analyzed using regression analysis. All statistical analyses were conducted with SAS software version 9.2. We calculated distance by using a Geographic Information System (ArcGIS version 10.0). The geometric mean blood lead level was 1.55 ${\mu}g/dL$ (boys: 1.59 ${\mu}g/dL$, girls: 1.51 ${\mu}g/dL$), and the geometric mean urinary cadmium level was 0.51 ${\mu}g/g$ creatinine (boys: 0.45 ${\mu}g/g$ creatinine, girls: 0.58 ${\mu}g/g$ creatinine). In the results of regression analyses, we found that urinary cadmium levels significantly decreased as distance between residence and industrial complex increased after adjusting for age, gender, income, passive smoking and the length of residence. This result was opposite to that for lead levels. Our observations support the hypothesis that urinary cadmium levels in children are related to their proximity to an industrial complex.

• The Korean Journal of Zoology
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• v.30 no.2
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• pp.99-106
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• 1987

It is the purpose to investigate the physiological toxity and mutagenicity by heavy metal compounds such as potasium dichromate, sodium arsenite and selenium dioxide on the development of Drosophila melanogaster. These chemical compounds were highly toxic at every developmental stage of Drosophila. The relative values of fecundity, viability and developmental time obtained on food media containing 5 different levels of potasium dichromate (500, 600, 700, 800, and 900 ppm), also 5 different levels of sodium arsenite and selenium dioxide (10, 15, 20, 25 and 30 ppm). Resulting in the relative values of fecundity and viability generally decreased, on the contrary developmental time generally reduced as the concentration of chemicals in the food increased. A significant reduction in the fecundity was observed between 800 and 900 ppm (p<0. 01) on the potasium dichromate media, between 15 and 20 ppm (p<0. 05) on the sodium arsenite media, between 20 and 25 ppm (p<0. 02) on the selenium dioxide media. A significant reduction in the viability was observed between 700 and 800 ppm (p<0. 01) on the potasium dioxide media, between 25 and 30 ppm (p<0. 01) on the sodium arsenite media, between 20 and 25 ppm (p<0. 01) on the selenium dioxide media. The developmental time was significantly reduced between 800 and 900 ppm (p<0. 001) on the potasium dioxide media, between 15 and 20 ppm (p<0. 001) on the sodium arsenite media, and between 25 and 30 ppm (p<0. 01) on the selenium dioxide media.

• Journal of Environmental Health Sciences
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• v.45 no.5
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• pp.559-560
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• 2019

• Journal of Korea Foundry Society
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• v.10 no.1
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• pp.43-49
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• 1990

The influences of Cu and Mg addition on wear properties of SiC particulate reinforced Al-Si metal(alloy) matrix composites were investigated. Metal matrix composites were prepared by combination of compocasting and hot pressing techniques. The main results obtained are as follows : 1) The composite with Mg addition exhibits letter wear resistance than that with Cu addition. It is considered that Mg addition improved wettability of matal matrix composite by the strong segregation to the SiC / Al matrix interface. 2) After homogenization treatment, it was found that the interfacial segregation of Mg was predominant, while that of Cu was not detected. 3) The SiC / Al-11Si eutectic composite exhibits better wear resistance than the SiC / Al-6Si hypoeutectic composite does. 4) It seems that the increase in the amount of Mg addition affects on the uniform dispersion of SiC particulates, on the refinement of microstructure and on age hardening and these effects cause wear resistance improvement of composites.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.974-978
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• 2008

Removal of heavy metal ions ($Cd^{2+}$ and $Zn^{2+}$) by electrocoagulation (ECG) was investigated in an acidic condition, which is necessary for re-using or discharging the mediated electrochemical oxidation (MEO) media. Effects of various parameters such as electrolytes, current densities, and electrode materials were examined for a metal-contaminated MEO system using $Fe^{2+}/Fe^{3+}$ pairs as a mediator. It was found that ECG with Al electrodes is greatly affected by the presence of $Fe^{2+}$. [$Cd^{2+}$] and [$Zn^{2+}$] remain constant until [$Fe^{2+}$] reaches a certain concentration level (ca. 10 mM). This preferential removal of $Fe^{2+}$ during ECG with Al electrodes is not alleviated by controlling current densities, potential programs, and solution mixing. ECG with Fe electrodes, on the other hand, resulted in relatively fast removal of $Cd^{2+}$ and $Zn^{2+}$ under coexistence of $Fe^{2+}$, indicative of the different role between $Fe^{n+}$ generated from an electrode and $Fe^{2+}$ initially present in a solution. When ECG was performed with Fe electrodes until [$Fe^{n+}$] became the same as the concentration of initially present $Fe^{2+}$, [$Cd^{2+}$] and [$Zn^{2+}$] were reduced to one-tenth of the initial concentrations, suggesting the possibility of a continuous use of the medium for a subsequent MEO process.

• Journal of Society of Preventive Korean Medicine
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• v.13 no.2
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• pp.77-87
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• 2009

Purpose : To evaluate the effects of Samultang(SMT) on the metals in the dams and fetuses Method : SMT(Decoction) was administered orally using different concentrations to pregnant Sprague-Dawley rats for 20days after being assigned randomly to 5 groups. Each group has 11 dams. Pregnant rats were sacrificed at the 20th day of gestation and metal concentration in the dams and fetuses was observed using a ICP-MS and mercury analyzer. Results : Hg concentration in the blood of dams was lower in the $SMT{\times}1$, $SMT{\times}2$, $SMT{\times}4$group than VC(Vehicle Control) and Control group. Hg concentration in the organs of dams was lower in the $SMT{\times}1$, $SMT{\times}2$, $SMT{\times}4$ group than VC, Control group. Whereas Cd concentration in the organs of fetuses was getting lower as increasing SMT dose, Hg concentration in the organs of fetuses was getting higher as increasing SMT dose. Discussion and Conclusion : There were not any significant harmful differences of metal concentration in the dams and fetuses treated by SMT. Particularly, SMT showed the possibility of efficacy to reduce the concentration of Hg in dams but to increase the concentration of Hg in fetuses. The mechanism of reduction is not yet proven. A hypothesis says there is a possibility of the chelation effect between the essential elements of herbs and heavy metals. Another hypothesis is the possibility of Hg transmission from dam to fetus. Further study should be conducted to make guidelines for the safe use of herbal medicine.

• Korean Journal of Environmental Agriculture
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• v.29 no.1
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• pp.61-65
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• 2010

Phytoextraction is a method of phytoremediation using plants to remediate metal-contaminated soils. Recently, various chelating agents were used in this method to increase the bioavailability of metals in soils. Even though phytoextraction is an economic and environment-friendly method, this cannot be applied in highly metal-contaminated areas because plants will not normally grow in such conditions. This research focuses on identifying chelating agents which are biodegradable and applicable to highly metal-contaminated areas. Lead (Pb) as a target metal and cysteine (Cys), histidine (His), citrate, malate, oxalate, succinate, and ethylenediamine (EDA) as biodegradable chelating agents were selected. Ethylenediamine tetraacetic acid (EDTA) was used as a comparative standard. Plants were grown on agar media containing various chelating agents with Pb to analyze the effect on root growth. Cys strongly increased the inhibitory effect of Pb on root growth of plants, while, His did not affect on it significantly. The inhibitory effect of oxalate is weak, and malate, citrate, and succinate did not show significant effects. Both EDTA and EDA diminished the inhibitory effect of Pb on root growth. The effect of EDA is correlated with decreased Pb uptake into the plants. In conclusion, as biodegradable chelating agents, EDA is a good candidate for highly Pb-contaminated area.

• Korean Journal of Ecology and Environment
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• v.40 no.4
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• pp.489-494
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• 2007

Transcriptional modulation of metallothionein (MT) during acute metal exposures (cadmium, copper or zinc) was examined in fry of Hemibarbus mylodon, a threatened fish species in Korean peninsula. Viability of H. mylodon fry was most affected by copper exposure (up to 79% of mortality at 1 ppm for 48 hours) and considerably by cadmium exposure (21 to 54% of mortality). On the other hand, Zn showed the least adverse effect on the viability (0 to 13% of mortality) of this species. Based on the semi-quantitative RT-PCR analysis, the stimulation of MT mRNA in response to metal exposures followed generally in a dose-dependent fashion where cadmium was the most potent inducer for the induction of MT transcripts in fry (up to more than 5-fold) while the lowest response was observed in zinc-exposed group (2-fold at maximum). From the exposure using environmentally realistic doses of cadmium (0 to 0.05 ppm for 24 hours), MT expression at mRNA level was also sensitively modulated toward upregulation up to more than 3-fold as relative to non-exposed control. Results from the present study would be a good basis for understanding the adaptive capacity and stress physiology of this endangered fish species during metal pollution.