• Tribology and Lubricants
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• v.26 no.4
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• pp.246-253
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• 2010

Friction characteristics of the brake friction materials without environmentally regulated ingredients were examined to find their role in the brake performance. Five friction materials were produced based on a nearcommercial formulation by changing the relative amount of potentially hazardous ingredients to health and environment, such as $Sb_2S_3$, potassium titanate, and brass fiber. Tribological properties of the friction materials were obtained using a scale dynamometer and Krauss type tribometer. Results showed that the excluded three ingredients played important synergetic effects on tribological properties in terms of fade resistance, wear resistance and friction effectiveness. In particular, brass fibers played important roles in the friction stability by providing excellent thermal diffusivity at the friction interface. Potassium titanate whiskers showed excellent fade resistance and wear resistance compared to the substituted barite. Antimony trisulfide, on the other hand, showed little effect on the high temperature fade resistance and wear resistance, while it increased friction effectiveness at moderate temperatures. The friction materials without the three ingredients showed severe fade, indicating antisynergy effects.

• Journal of Nutrition and Health
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• v.33 no.7
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• pp.733-738
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• 2000

The purpose of this study was to investigate the effects of green tea on gene expression of superoxide dismutase(SOD) and glutathione peroxidase(GSH-Px) in rat liver exposed to microwave. Sprague-Dawley male rats with 200$\pm$10g body weight were assigned to normal and microwave exposed groups : microwave exposed groups ; microwave exposed groups were divided two groups : microwave(MW) group which was administrated the distilled water and green tea(GT) group which was administrated the green tea extracts. The rats were irradiated with microwave at frequence of 2.45 GHz for 15 min and then the gene expression in the damaged tissue were investigated at 0.1, 3, 4,6 and 8 days after the microwave irradition to compared with the normal group. The level of SOD gene expression in MW group was lower than the normal group within 6 days but that of GT group as higher than MW group. These results may imply that green tea stimulates SOD expression and there by protecting tissues from free radicals. The GSH-Px gene was expressed a little bit lower than the normal group but that of GT group was expressed to higher lever than MW group from 4 days after irradiation. These results suggest that the administration of green tea extract may activate antioxidative gene expressions such as SOD and GSH-Px in rat and that may help to recover liver tissues from microwave damage by removing hazardous free radicals and oxidized by products from cells.

• The Journal of Engineering Geology
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• v.10 no.1
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• pp.39-50
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• 2000

Because of numerous mountain region, agricultural affairs work can't be done without groundwater in Kangwon Do area. Especially to improve high mountain area vegetable quality and raise income offarmers, both of groundwater and hydrothermal system to keep adequate temperature in hot and coldseason have to be developed. Domestic groundwater was developed for the use of agricultural watersince 1960. Exact investigation and control of groundwater are greatly required in utilizing undergroundspace as subway, nuclear power plant, oil and hazardous waste storehouse. Groundwater contaminationowing to industrial irrigation, trash decomposition can have a serious effect on human health and rustof underground building. In this study, global prospecting system are applied to detect groundwater, using electrical, seismic and georadar prospecting method.

• Korean Journal of Environmental Agriculture
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• v.21 no.3
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• pp.223-228
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• 2002

In addition to supplying the essential elements, Ca and S, phosphogypsum can have profound effect on both the physical and chemical properties of certain soils. However, no widespread use of by-product phosphogypsum will be made unless such uses pose no threat to the public health and soil contamination. In this study, the extractability of As, Cd, Cu, and Pb with water and DTPA solution from phosphogypsum samples of pH 3, 5, and 7 were investigated to estimate the availability of those metals. Contents of water extractable metals in ohosphogypsum were less than 5 mg/kg for all the heavy metals investigated. The extractability of metals in DTPA solution was not quite different but a little higher in comparison to the water extraction. And the extractability was decreased as the pH of phosphogypsum increased. In the phosphogypsum of pH 7, amounts of water extractable metals were nearly zero. There was no significant difference in the amount of extractable metals during the extraction period of 5 weeks. The length of extraction time did not affect heavy metal extractability. Therefore there may be small fractions of easily soluble or extractable forms of metals in the phosphogypsum and most of the metals would be present in very insoluble forms. These results suggest that the application of phosphogypsum at appropriate rates on agricultural lands appears of no concern in terms of hazardous element contamination in soil.

• Journal of the Korean Society of Safety
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• v.27 no.3
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• pp.63-70
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• 2012

In the hazardous areas where explosive gases, vapor or mists exist, electrical apparatus and installations must be the explosion-proof construction to prevent or limit the danger of the ignition of potentially explosive atmosphere. In Korea, nine types of protection have been specified in the government regulations at present: flameproof enclosure, pressurization, oil immersion, increased safety, intrinsic safety, non-incendive, powder filling, encapsulation, and special types. Among these types, the intrinsic safety has the construction which limit or by-pass igniting the electric energy using electronic devices. This type has lots of merits but at the same time requires a high-degree of technology. In this paper, we investigated several dominating factors which affect the minimum ignition energy; this energy plays a very important role in design and evaluation of the intrinsic safety type electrical apparatus. Electrode material, which is one of the most important factors, was intensively studied for the five sorts of material(Al, Cd, Mg, Sn, and Zn) with performing experiment in a low-voltage inductive circuit using IEC-type(International Electro-technical Commission) spark apparatus. The experimental results show that the minimum ignition energy of electrode material is varied: highest in Cd and lowest in Sn. We also confirmed the effect of electrode make-and-break speed.

• Journal of Industrial Technology
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• v.39 no.1
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• pp.41-45
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• 2019

Hydrogen sulfide ($H_2S$) is mainly produced along with methane and hydrocarbons in many gas fields as well as hydrodesulfurization processes of crude oils containing sulfur compounds and the emission of $H_2S$ has a considerable effect on both environmental problem and human health aspects due to formation of, e.g. acid rain and smog. In recent years, ionic liquids (ILs) have been proposed as the most promising solvents for $CO_2$ and hazardous pollutants capture, such as $H_2S$ and sulfur dioxide ($SO_2$). In this work, we demonstrate the use of the predictive COSMO-SAC model for the prediction of Henry's law constant of $H_2S$ in ILs. Furthermore, the method is used to screen for potential IL candidates for $H_2S$ capture from a set of 2,624 ILs formed from 82 cations and 32 anions. The effects of cation on the Henry's law constant of $H_2S$ such as (i) the variation of the alkyl chain length on cation, (ii) the substituent of methyl group ($-CH_3$) for H in C(2) position and (iii) the change of ring structure for cation family are clearly predicted by COSMO-SAC model.

• Journal of the Korean Applied Science and Technology
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• v.36 no.1
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• pp.333-340
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• 2019

This paper was described about the preparation of the multi-functional mask pack and its evaluation. Here, the multi-functional effects means the far-infrared emissivity effect due to polyphosphoric acid, the freckles treatment effect and peeling effects due to inclusion complexes, and the skin temperature decreasing effect due to Lavender-extraction compounds. The the hazardous chemicals, viscosity, and pH were determined blow 0.01%, 280 cP, and pH=6.92 in the prepared multi-functional mask pack solution, respectively. The multi-functional mask pack prepared with dipping method in the solution were showed the value of $0.882{\mu}m$ (Far-infrared emissivity) and $3.40{\times}10^2W/m$ at $37^{\circ}C$ (Far-infrared radiation energy), respectively. After taking multi-functional mask pack, the skin moisturizing rate was indicated 35.5%, and the skin temperature was showed in the range of $24{\sim}26^{\circ}C$. The skin stimulation test for the 30 volunteer was showed very strong stability.

• Korean Journal of Food Science and Technology
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• v.42 no.4
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• pp.390-397
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• 2010

Residual solvents in foods are defined as organic volatile chemicals used or produced in manufacturing of extracts or additives, or functional foods. The solvents are not completely eliminated by practical manufacturing techniques and they also may become contaminated by solvents from packing, transportation or storage in warehouses. Because residual solvents have no nutritional value but may be hazardous to human health, there is a need to remove them from the final products or reduce their amounts to below acceptable levels. The purpose of this study was to develop and evaluate an analytical method for the screening of residual solvents in health functional foods. Furthermore, the aim of this study was to constitute a reasonable management system based on the current state of the market and case studies of foreign countries. Eleven volatile solvents such as MeOH, EtOH, trichloroethylene and hexane were separated depending on their column properties, temp. and time using Gas Chromatography (GC). After determining the GC conditions, a sample preparation method using HSS (Head Space Sampling) was developed. From the results, a method for analyzing residual solvents in health functional foods was developed considering matrix effect and interference from the sample obtained from the solution of solvents-free health functional foods spiked with 11 standards solutions. Validation test using the developed GC/HSS/MS (Mass Spectrometry) method was followed by tests for precision, accuracy, recovery, linearity and adequate sensitivity. Finally, examination of 104 samples grouped in suits was performed by the developed HSS/GC/MS for screening the solvents. The 11 solvents were isolated from health functional foods based on vapor pressure difference, and followed by separation within 15 minutes in a single run. The limt of detection (LOD), limit of quantification (LOQ), recovery and coefficient of variation (C.V.) of these compounds determined by the HSS/GC/MS were found to be 0.1 pg/mL, 0.1-125 pg/g, 51.0-104.6%, and less than 15%, respectively. Using the developed HSS/GC/MS method, residual solvent from 16 out of 104 health functional products were detected as a EtOH. This method therefore seems t o be a valuable extension ofanalytical method for the identification of residual solvents in health functional food.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.2
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• pp.292-300
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• 1996

Hexavalent chromium($Cr^{+6}$) compounds are considered to be particularly hazardous, primarily because of the associated risk of allergic reaction and cancer. The analytic method of hexavalent chromium such as the s-diphenylcarba-zide(DPC) method and all ether previously used methods are often made uncertain due to significant interferences from organic components. This report can provide a technique for the more rapid and simple determination of total hexavalent chromium. than other currently using methods. The s-diphenylcarbazide method proposed by the U.S. National Institute for Occupational Safety and Health has low recovery rate(15.67 - 48.20%) due to interference, iron chloride and nickel chloride. A microwave oven technique has high recovery rate(about 70%) of insoluble hexavalent chromium. For the difference of ionic charges of $Cr^{+3}$-ethylenediamine tetraacetic acid(EDTA) chelate and $CrO_4{^{-2}}$, we could detect them simultaneously by ion exchanged high performance liquid chromatography. The confirmation of $Cr^{+3}$ and $Cr^{+6}$ were checked by fraction collector and flameless atomic absorption spectrometer. We observed that the small amount of hexavalent chromium is converted to trivalent chromium due to enhancement of chromium reduction by $Fe^{+3}$ or $Ni^{+2}$. As a result of this study, on the analysis of insoluble hexavalent chromium with microwave oven was used for, it may be better and more precise analysis after pretreatment by 2% NaOH-3% $Na_2CO_3$ and then analysis UV-spectrophotometer. It should be done for various studies on insoluble hexavalent chromium on the basis work environmental monitoring so called welding, painting etc.

• Journal of Environmental Health Sciences
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• v.44 no.6
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• pp.548-555
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• 2018

Objectives: We conducted ecological risk assessment for cadmium, a heavy metal and carcinogen, to identify safety standards by environmental media and to determine its impact on ecosystems by estimating and evaluating exposure levels. Methods: Species sensitivity distributions (SSDs) were generated using ECOTOX DB. A hazardous concentration of 5% (HC5) protective of most species (95%) in the environment was estimated. Using this estimate, predicted no effect concentrations (PNECs) were calculated for aquatic organisms. Based on the calculated PNECs for aquatic organisms, PNEC values for soil and sediment were calculated using the partition coefficient. Predicted exposure concentrations (PECs) were also calculated from environmental monitoring data with hazard quotients (HQs) calculated using PNECs for environmental media. Results: Chronic toxicity data were categorized into four groups and 11 species. In species sensitivity distribution (SSD) analysis, HC5 was $0.340{\mu}g/L$. Based on this value, the PNEC value for aquatic organisms was calculated as $0.113{\mu}g/L$. PNEC values for soil and sediments using a partition coefficient were calculated as 15.02 mg/kg and 90.61 mg/kg, respectively. In an analysis of environmental monitoring data, PEC values were calculated as $0.017{\mu}g/L$ for water, 1.01 mg/kg for soil, and 0.521 mg/kg for sediment. Conclusions: HQs were 0.150, 0.067 and 0.006 for water, soil and sediment, respectively. HQs of secondary toxicity were 0.365 for birds and 0.024 for mammals. In principle, it is judged that an HQ above 1 indicates a high level of risk concern while an HQ less than 1 indicates an extremely low level of risk concern. Therefore, with HQs of cadmium in the environment being <1, its risk levels can be considered low for each media.