• Journal of Korean Society of Water and Wastewater
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• v.19 no.1
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• pp.31-37
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• 2005

One of the major obstacles confronted in promoting the rainwater harvesting is the concerns of acid rain and heavy metals. Although there are many data concerning the quality of rainwater precipitation for the study of acid rain, the study on the quality of stored rainwater has been limited. In this study, we monitored the quality of stored rainwater at Galmoe middle school, where a rainwater harvesting system is installed and in use for more than two years. We measured water quality parameters such as pH, Electro Conductivity(EC), Dissolved Oxygen(DO), and some metals (aluminium (Al), chromium(Cr), manganese(Mn), zinc(Zn), copper(Cu), arsenic(As), cadmium(Cd), lead(Pb)). The monitoring period was during one year from September 9th 2003 to August 5th 2004. It was observed that the average pH of stored rainwater is neutral. DO is similar to tap water and EC is lower than tap water. Metal Concentrations are within the concentration specified in Drinking Water Quality Standard. Overall, the stored rainwater quality is good enough for sundry use and there's no threat of acid rain and air pollution, if the rainwater harvesting system is well designed and maintained.

• Journal of the Mineralogical Society of Korea
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• v.10 no.2
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• pp.139-147
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• 1997

The Janghang smelter is the first lead, zinc and copper smelting facility in Korea which was operated for a half century from 1936 to 1989. The clay minerals and their heavy metal association in the soil profile around the smelter have been studied using XRD, EPMA, SEM-EDS, TEM, EPR and sequential extraction techniques. The soils in A horizon are highly acidic showing pH 4.45. The pH is going up with increasing depth. They have residual water contents of 1.18-1.51 wt%, loss on ignition of 6.32-7.79 wt%, and carbon contents of 0.08-0.88 wt%. Soils consist of quartz, feldspar, muscovite, kaolinite, vermiculite, biotite, chlorite, goethite and hematite in the decreasing abundance. The contents of clay minerals, especially vermiculite and chlorite, decrease with increasing depth. Sequential extraction experiments for the profile samples show that heavy metals (Zn, Cu, Pb, Cd) are highly concentrated in the A horizon of the soil profile as water-extractable (mostly amorphous), MgCl2-extractable (exchangeable in clay minerals), and organic phases. The heavy metal contents decrease with increasing depth. It suggests that the heavy metals are mainly associate with clay minerlas in an exchangeable state. It is also noted that heavy metals are highly concentrated in the manganese and iron oxide phases.

• Journal of Environmental Health Sciences
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• v.22 no.2
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• pp.83-89
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• 1996

In order to evaluate the air quality, dry and wet deposition samples were collected by deposit containers during four months in Inchon area. The samples were analyzed for its solid composition and trace elements(Ca, Cd, Cu, Fe, Mn, Ni, Pb, Zn). The main results are summarized below 1. The amounts of dry and wet deposition in Inchon area were 1.06~3.14 ton/$km^2$/month, and affected by the rainfall and suspended yellow sand. 2. Through the analysis of solid balance, we found that 50% of total solids(TS) was fixed suspend ed solids(FSS), 25% was fixed dissolved solids(FDS), and each of volatile suspended solids(VSS) and volatile dissolved solids(VDS) accounted for 12.5%. 3. The amounts collected by sampler for trace elements were 938 ~ 2,765 $\mu g$ calcium/10days sampler, 0.2 ~ 90.4 $\mu g$ cadmium/10days/sampler, 26 ~ 298 $\mu g$ copper/10days/sampler, 928 ~ 3,939 $\mu g$ iron/10days/sampler, 50 ~ 202 $\mu g$ manganese/10days/sampler, 4 ~ 37 $\mu g$ nickel/10days/sampler, 52 ~ 406 $\mu g$ lead/10days/sampler, and 97 ~ 1,317 $\mu g$ zinc/10days/sampler, respectively. 4. Using the manganese analysis, it was found that 76.1% of TS was from soil.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.5
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• pp.416-421
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• 2011

Nowadays, the increasing demands upon mobile devices such as wireless sensor networks and the recent advent of low power electrical devices such as MEMS make such renewable power sources attractive. A vibration-driven MEMS lead zirconate titanate $Pb(Zr,Ti)O_3$ (PZT) cantilever device is developed for energy harvesting application. This paper presents a piezoelectric based energy harvester which is suitable for power generating from conventional vibration and has in providing energy for low power electron ic devices. The PZT cantilever is used d33 mode to get the electrical power. The PZT cantilever based energy harvester with the dimension of 7 mm${\times}$3 mm${\times}$0.03 mm is fabricated using micromachining technologies. This PZT cantilever has the mechanical resonance frequency with a 900 Hz. With these conditions, we get experimentally the 37 uW output power from this device with the application of 1g acceleration using the 900 Hz vibration. From this study, we show the feasibility of one of energy harvesting candidates using PZT based structure. This PZT energy harvester could be used for various applications such a batteryless micro sensors and micro power generators.

• Journal of radiological science and technology
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• v.41 no.2
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• pp.135-140
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• 2018

In this study, the dose of antimony shielding sheet was measured and the shielding rates according to the distance between the radioisotopes and the detector was analyzed according to the type of $^{99m}Tc$, $^{18}F$, $^{201}Tl$, $^{131}I$, $^{123}I$ using the antimony shielding sheet. The detector was used with an inspector. Six sheets of 0.25 mmPb were prepared with 20 cm width and length. Measurement results using $^{99m}Tc$, $^{201}Tl$, and $^{123}I$ showed that as the thickness of the sheet became thicker, the farther the distance from the source to the sheet was, the smaller the transmitted dose amount was measured. It was analyzed that a thickness of 1.50 mm or more was required to obtain a shielding rates of 90% or more. In the experiments of $^{18}F$ and $^{131}I$, the dose value was highest when 0.25 mm sheet was used, and the shielding rates was negative, unlike the results of other radioisotopes. Since $^{201}Tl$ are used when using antimony sheet and $^{18}F$ and $^{131}I$ have no shielding effect, it is thought that it is effective to reduce dose by repeating training and simulation training so that work can be done in a short time.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.475-480
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• 2002

The reliability of the solder joint is affected by type and extent of the interfacial reaction between solder and substrates. Therefore, understanding of intermetallic compounds produced by soldering in electronic packaging is essential. In-based alloys have been favored bonding devices that demand low soldering temperatures. For photonic and fiber optics packaging, m-based solders have become increasingly attractive as a soldering material candidate due to its ductility. In the present work, the interfacial reactions between indium solder and bare Cu Substrate are investigated. For the identification of intermetallic compounds, both Scanning Electron Microscopy(SEM) and X-Ray Diffraction(XRD) were employed. Experimental results showed that the intermetallic compounds, such as Cu$_{11}$In$_{9}$ was observed for bare Cu substrate. Additionally, the growth rate of these intermetallic compounds was increased with the reaction temperature and time. We found that the growth of the intermetallic compound follows the parabolic law, which indicates that the growth is diffusion-controlled.d.

• Journal of Environmental Health Sciences
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• v.20 no.4
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• pp.36-44
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• 1994

A study was carried out in order to investigate the removal efficiencies and removal characteristics of heaw metals such as Pb, Cd, Cr, Cu in raw water by one of conventional water treatment processes. The coagulants used in this study were Alum and PAC. Three kinds of water samples were provided: kaolin water, kaolin water mixed with humic acid and raw water from Han River mixed with suspended matter deposited on raw water inlet pipe. Heaw metals were added to the water samples with their respective turbidity, and jar tests were performed. In the results from heaw metal removal studies, lead might be adsorbed or exchanged on the particle surface (SS) rather than react with organic matter added. Cadmium was affected on the dissolved organic matter. Chromium was affected by the both dissolved organic matter and SS concentration, and the restabilization and the enmeshment appeared at moderate (50~80 NTU) and high (100 NTU) turbidity as defined in this experimenL The removal efficiency of copper was relatively little affected by the dissolved organic matter but by SS concentration in comparison with other heavy metals. In these studies as to the raw water turbidities and concentration of heaw metals, it is proved out that the removal efficiency on heaw metals in both cases of PAC and Alum as coagulants was not significantly different.

• Journal of Environmental Science International
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• v.15 no.11
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• pp.1053-1059
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• 2006

This study was performed to investigate the possible uses of waste sludge for the removal of heavy metal ions. The adsorption experiments were conducted with wastes such as sewage treatment sludge, water treatment sludge and oyster shell to evaluate their sorption characteristics. Heavy metals selected were cadmium, copper and lead. in the sorption experiments on the sewage treatment sludge, water treatment sludge, oyster shell and soil, sorption occurred in the beginning and it reached equilibrium after 40 minutes on the oyster shell and 4 hour on the sewage treatment sludge and water treatment sludge. Results of Freundlich isotherms indicated that sewage treatment sludge could be properly used as an adsorbent for heavy metals and sorption strength of heavy metals was in the order of Pb > Cu > Cd. In the influence of pH on the adsorbents, sorption rate was more than 80% in pH 4 and most of heavy metals were adsorbed in pH 9. Adsorption rate of Cd decreased with decreasing pH and then adsorption rate of Cu was lower in soil.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.9
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• pp.429-433
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• 2006

PZT(80/0) powder was prepared by a sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The coating and drying procedure was repeated 4 times. And then the PZT(20/80) precusor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5mol/L and the number of coating was varied from 0 to 6. The porosity decreased and the grain size increased with increasing the number of coatings. The thickness of the PZT-6(6: number of coatings) films was about $60{\mu}m$. The relative dielectric constant increased and the dielectric loss decreased with increasing the number of PZT(20/80) sol coatings. The relative dielectric constant and dielectric loss of the PZT-6 thick film were 275 and 3.5%, respectively. The remanent polarization, coercive field and breakdown strength of the PZT-6 film were $19.8{\mu}C/cm^2$, 13.7kV/cm and 130kV/cm, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.387-391
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• 2004

[ $(Bi_{1/2}Na_{1/2})TiO_3$ ](BNT) is considered to be an excellent candidate for the key material of lead-free piezoelectric ceramic due to properties of strong ferroelectricity with a relatively large remanent polarization $Pr=38{\mu}C/cm^2$, and a large coercive field, Ec=73KV/cm. In this study, electrical properties of pressure sensor using a $0.96Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}TiO_3+0.04SrTiO_3+0.2wt%La_2O_3$ ceramics are investigated. Resonant frequency of pressure sensor was decreased with increasing pressure. However, its anti-resonant frequency was increased with increasing pressure.