• Economic and Environmental Geology
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• v.37 no.1
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• pp.61-72
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• 2004

The soil samples were collected from the paddy field near the mine tailing dumps in the abandoned Duckum mine in Korea. In the laboratory, the soil solution was extracted from the soil using centrifuge, and analysed for the chemical composition. Physical and chemical soil properties were also analysed. Kaolinite is the main clay minerals in the paddy soil and the CEC value is therefore relatively low. Nearly all soil samples show enrichment in their trace elemental concentrations(Cd, Cu, Pb and Zn) compared with natural background level. Some soil samples exceed the soil remediation intervention values for Cd, Pb and Zn and target value for Cu, when compared with Dutch standard, whereas As, Ni and Cr are in normal range. Lead concentrations in some samples near the mine tailing dumps also exceed the standard for remediation act for agricultural area set by Korean soil conservation law. The trace elemental concentrations are higher in the paddy soil nearer the mine tailing dumps and lower for the samples from distance. Similar trend with distance is found for the soil solution chemistry but the decrease with distance from the mine tailing dumps are sharper than the changes in soil chemistry. Cadmium, Cu and Pb concentrations in the soil solution are very low, ranging from a tenth and hundredths to a maximum of several mg/l, whereas their concentrations in soils are highly enriched for natural background. Most of the trace elements are thought to be either removed by reduced iron sulphides or iron oxides, depending on the redox changes. Geochemical equilibrium modelling indicate the presence of solubility controlling solid phases for Cd and Pb, whereas Zn and Cu might have been controlled by adsorption/desorption processes. Although pollutants migration through solution phase are thought to be limited by adsorption onto various Fe, Mn solid phases, the pollutants exist as easily releasable fractions such as exchangeable site. In this case, the paddy soil would act as pollutant pool, which will supply to plants in situ. whenever the geochemical conditions favour.

• Korean Journal of Heritage: History & Science
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• v.14
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• pp.225-250
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• 1981

The investigation of air fungal population in the storages to keep papers and textiles that are designated as important folk life materials or treasures was carried out from Dec. 17 to. 23, 1980. Isolation media was used for malt extract agar with chloramphnicol to prevent bacterial contamination. Isolation and identification of air fungi from the four preserved rooms were Cladosporium cladosporioides, Alternaria chlamydospora, Aspergillus fumigatus, A. versicolor, Eurotium chevalieri, Penicillium charlesii var. rapidum, P. oxalicum. P. viridicatum, Trichoderma viride, Acremomium sp., Mucor sp. and Yeast. It was found that nine species in eight genera was isolated. Among them, underscribed species in Korea was two species ; Eurotium chevalieri and Penicillium visidicatum. The fungal population of four storages was showed to be dominant species such as Cladosporium cladosporioides and the order was Acremonium, Penicillium, Aspergillus, Trichoderma, Alternaria and Eurotium. Eurotium chevalieri was ascomycetous fungi including distinctive ascospores in cleistothecia, the filamentous fungi was directly isolated from the papers and cellulose materials showing to be fourteen species in eight genera. The most species of the fungi isolated was also Cladosporium cladosporioides and the other fungi were found as Acremonium, Penicillium, Aspergillus and Trichoderma. It was confirmed that underscribed fungi were two species ; Mucor racemosus and Penicillium spinulosvm. The effect of four antifungal agents, benzoic acid, sorbic acid, dehydroacetic acid and thymol was also examined on eight species of Aspergillus, Penicillium, Cladosporium. and Tricoderma. this results were shown that more than 0.5% concentration of thymol inhibited the grow of all fungalspecies and other three chemicals appeared various inhibition zones of fungal growth depending in their different concentrations.

• International Journal of Ocean System Engineering
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• v.2 no.3
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• pp.185-194
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• 2012

A Macroscopic combination of two or more distinct materials is commonly referred to as a "Composite Material", having been designed mechanically and chemically superior in function and characteristic than its individual constituent materials. Composite materials are used not only for aerospace and military, but also heavily used in boat/ship building and general composite industries which we are seeing increasingly more. Regardless of the various applications for composite materials, the industry is still limited and requires better fabrication technology and methodology in order to expand and grow. An example of this is that the majority of fabrication facilities nearby still use an antiquated wet lay-up process where fabrication still requires manual hand labor in a 3D environment impeding productivity of composite product design advancement. As an expert in the advanced composites field, I have developed fabrication skills with the use of machinery based on my past composite experience. In autumn 2011, the Korea government confirmed to fund my project. It is the development of a composite sanding machine. I began development of this semi-robotic prototype beginning in 2009. It has possibilities of replacing or augmenting the exhaustive and difficult jobs performed by human hands, such as sanding, grinding, blasting, and polishing in most often, very awkward conditions, and is also will boost productivity, improve surface quality, cut abrasive costs, eliminate vibration injuries, and protect workers from exposure to dust and airborne contamination. Ease of control and operation of the equipment in or outside of the sanding room is a key benefit to end-users. It will prove to be much more economical than normal robotics and minimize errors that commonly occur in factories. The key components and their technologies are a 360 degree rotational shoulder and a wrist that is controlled under PLC controller and joystick manual mode. Development on both of the key modules is complete and are now operational. The Korean government fund boosted my development and I expect to complete full scale development no later than 3rd quarter 2012. Even with the advantages of composite materials, there is still the need to repair or to maintain composite products with a higher level of technology. I have learned many composite repair skills on composite airframe since many composite fabrication skills including repair, requires training for non aerospace applications. The wind energy market is now requiring much larger blades in order to generate more electrical energy for wind farms. One single blade is commonly 50 meters or longer now. When a wind blade becomes damaged from external forces, on-site repair is required on the columns even under strong wind and freezing temperature conditions. In order to correctly obtain polymerization, the repair must be performed on the damaged area within a very limited time. The use of pre-impregnated glass fabric and heating silicone pad and a hot bonder acting precise heating control are surely required.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.4
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• pp.288-295
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• 2010

Metal exposure experiments using polychaete (Perinereis nuntia) as a bio-indicator of trace metals contamination were conducted to evaluate the bioaccumulation and the biomarkers responses such as metallothionein-like protein (MTLPs) and glutathione S-transferase (GST) which was simultaneously exposed to Cadmium (Cd) and Copper (Cu). Cu and Cd concentrations in polychaete were enhanced with increasing exposure time and their concentrations of aqueous medium. Initial accumulation of Cd was higher than that of Cu. Our results showed that the bioaccumulation of Cu and Cd were prohibited, especially at higher Cu levels, suggesting the different cellular uptake mechanisms when Cu and Cd are co-exist. Net accumulation rate of Cu was declined with exposure time but it did not show any significant change for Cd. Although the highest MTLPs concentration was observed at 6 hr of exposure time, it did not show any significant change related to exposure times and metals concentrations. An increase of GST activity tended to increase as a function of exposure time and metals concentrations. And GST activities in P. nuntia have similar tendency with bioconcentration factors in high concentration of Cu (treatment group IV) at post 24 h of exposure. Our results provide new information of the bioaccumulation and biomarker responses to understand the effects of co-existing contaminants (Cu and Cd) using polychaete. Further studies are required to elucidate the bioaccumulation and biomarkers responses for various contaminants.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.4
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• pp.65-69
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• 2009

Purpose: Recently incidence of VDT syndrome has gradually increased as extensive use of computers. VDT syndrome reported by VDT workers include musculoskeletal disorder, neuropsychiatric disoders and eye symptoms such as eye strain, tired eyes, irritation and blurred vision. The environmental factors of VDT syndrome include electromagnetic waves, size, brightness and lighting of computer screen, height of a monitor and a worktable, working hours, kind of task, distance between screen and workers, indoor humidity and temperature, indoor air contamination and ventilation. In this study, we investigated the environmental factors related to body symptoms and health effects included in VDT syndrome. Methods: Study subjects were total 120 persons (54 male, 66 female) with age from 19 to 28. We surveyed the body symptoms and physical discomfort when doing an activity in a short distance such as reading book or paper, computer work. The questionnaire included main body symptoms, self-consciousness symptoms of eye, satisfaction of working environment, pain of the wrist when using keyboard and mouse. Results: Most of people (70%) felt physical pain from long time work of computer, paper, electrical apparatus. They mainly complained pain of neck and low back (57.1%), eye (45.2%) and head (31%). With the environmental factors, 78.3% of the subjects complaint pain of eye from inappropriate illumination. Most of the symptoms included 'eye fatigue'(38.3%), 'dryness of eye'(31.9%) and 'blurred vision'(23.7%). Subjects in this study complained discomfort of their chairs and most of them experienced pain in the wrist when using keyboard or mouse. Conclusions: When people use electrical apparatus or work with paper, people would get their eye fatigue and feeling of physical fatigue because of not harmonizing various environmental factors such as light, space, posture, worktable with theirselves. Therefore, workers should develop preventive method such as self-control of adequate break time to avoid fatigue while VDT work. Work environment should be changed to ergonomic design for optimal visual environment to prevent musculoskeletal disorder through constant research.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.8
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• pp.420-427
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• 2016

This study was conducted on the sediment remediation using micro-bubble to remove fine particles. For this study, characteristics of contamination and release in sediment were analyzed. And then, the characteristics of bubbles on removal efficiency was investigated at various operation conditions. In particle size distribution of the sediment used for the study, the proportion of clay and silt (<0.075 mm) was about 7.7%, sand (0.075~4.75 mm) was about 67.8%, and gravel (${\geq}4.75$) was 24.5%. Total nitrogen (TN) and total phosphorus (TP) of the sediment were 2,790~3,260, 261~311 mg/kg respectively. Ignition loss and water content were 4.1~9.6, 32.9~53.2% respectively. In analysis of removal efficiency according to operation conditions of micro-bubble, it was the highest when operation condition is pressure 6 atm, pressurized water ratio 30%, and coagulant dosage 15 ppm. At the time, the sediment's removal efficiency was 19.9%. Accordingly removal efficiency of TN and TP were 21.4, 22.6% respectively. Finally a research was found that fine particles in sediment were almost removed by micro-bubble, which led to decrease nutrients' release at about 20.1~64.3% in comparison to sediment including lots of fine particles.

• Food Science and Preservation
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• v.14 no.1
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• pp.35-41
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• 2007

As the consumption of environmentally friendly agricultural products increases, food safety is at the forefront of public health concerns. We analyzed the biological hazards of 26 species of leaf vegetables and 4 species of fruit according to types of cultivation (conventional or organic filming) and distribution system (giant retailers or organic food stores) using various culture media, automatic bacterial identification systems, and microscopy, Total bacterial count of unwashed agricultural product ranged from $5.2{\times}10^{3}\;to\;1.5{\times}10^{5}\;CFU/mL$ (from 0.1 g of agricultural products), and the average count dropped 25-fold (range, 8-60-fold) after water washing. Microbial levels of washed organic agricultural products were $6.0{\times}10^{2}-1.9{\times}10^{4}\;CFU/mL$, and were not significantly different f개m the microbial loads on conventionally farmed produce. There was no significant difference in bacterial count from agricultural produce purchased from giant retailers or organic food stores. Total microbial count of Chinese cabbage, welsh onion, red chicory and kale were comparatively high, and Enterobacter cloacae was isolated most frequently. Parasites were detected in agricultural products purchased from conventional farm products in the stores of giant retailers, and in organic food stores, and parasite prevalence was especially high in Chinese cabbages and welsh onion. The study indicated that cultivation methods and distribution systems did not cause significant differences in biological contamination levels of agricultural produce. Some vegetables and fruits were highly contaminated effective sanitizing methods to reduce these biological hazards are needed.

• Journal of dental hygiene science
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• v.16 no.4
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• pp.284-292
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• 2016

Water supplied through dental unit waterlines (DUWLs) has been shown to contain high number of bacteria. To reduce the contamination of DUWLs, it is essential to develop effective disinfectants. It is, however, difficulty to obtain proper DUWL samples for studies. The purpose of this study was to establish a simple laboratory model for reproducing DUWL biofilms. The bacteria obtained from DUWLs were cultured in R2A liquid medium for 10 days, and then stored at $-70^{\circ}C$. This stock was inoculated into R2A liquid medium and incubated in batch mode. After 5 days of culturing, it was inoculated into the biofilm formation model developed in this study. Our biofilm formation model comprised of a beaker containing R2A liquid medium and five glass rods attached to DUWL polyurethane tubing. Biofilm was allowed to form on the stir plate and the medium was replaced every 2 days. After 4 days of biofilm formation in the laboratory model, biofilm thickness, morphological characteristics and distribution of the composing bacteria were examined by confocal laser microscopy and scanning electron microscopy. The mean of biofilm accumulation was $4.68{\times}10^4$ colony forming unit/$cm^2$ and its thickness was $10{\sim}14{\mu}m$. In our laboratory model, thick bacterial lumps were observed in some parts of the tubing. To test the suitability of this biofilm model system, the effectiveness of disinfectants such as sodium hypochlorite, hydrogen peroxide, and chlorhexidine, was examined by their application to the biofilm formed in our model. Lower concentrations of disinfectants were less effective in reducing the count of bacteria constituting the biofilm. These results showed that our DUWL biofilm laboratory model was appropriate for comparison of disinfectant effects. Our laboratory model is expected to be useful for various other purposes in further studies.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.39-53
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• 2001

Environmental pollution of the Tohyun mine creek area was investigated on the basis of geology, mineralogy and geochemistry. In soils and sediments of the mine area, ${Al_2}{O_3}/{Na_2O}$ and ${K_2}O/{Na_2}O$ ratios are partly negative correlation against ${SiO_2}/{Al_2}{O_3}$, respectively. Geochemical characteristics of some trace and rare earth elements such as V/Ni, Ni/Co, La/Ce, Th/Yb, Th/U, La/Th, ${La_N}/{Yb_N}$, La/Sc and Sc/Th are revealed a narrow range and homogeneous compositions may be explained by simple source lithology. These results suggest that sediments source of the host shale around the mine area could be originated by basic to intermediate igneous rocks. Mineral compositions of soil and sediment near the mine area were partly variable mineralogy, which are composed of quartz, mica, feldspar, chlorite, clay minerals and some pyrite. Soils and sediments with highly concentrated heavy minerals, gravity separated mineralogy, are composed of some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, goethite and various kinds of hydroxide minerals on the polished sections. As normalized by bed rock composition, average enrichment indices of major elements in sediments, precipitates, farmland soils and paddy soils are 1.0, 1.7, 0.9 and 0.8, respectively. Maximum concentration of environmental toxic elements in the mine creek are detected with Ag = 186 ppm, As = 17,100 ppm, Bi = ]27 ppm, Cd = 77 ppm, Cu = 12,299 ppm, Pb = 8,897 ppm, Sb = 1,350 ppm, W = 599 ppm and Zn = 12,250 ppm, which are increasing with total FeO increasing, and extremely high concentrations of surface sediments and precipitates near the waste rock dump. These toxic elements (As, Bi, Cd, Cu, Pb, Sb, W and Zn) of the samples, normalizing by host rock concentration, revealed that average enrichment index is 106.0 for sediments, 279.6 for precipitates, 3.5 for farmland soils and 1.6 for paddy soils. However, on the basis of EPA values, enrichment indices of all the samples are 40.7, 121.4, 1.3 and 0.6, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.3
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• pp.172-180
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• 1993

Chemical properties of the soils were surveyed in the field of vinyl houses concentrated in the area of Bunpyong-dong and Shinchon-dong of Cheongju, Chilgeum-dong of Chungju and Gageum-myeon of Jungweon-gun. Chungcheongbuk-do province. 1. Content of chemical component of the soil in the vinyl house was higher than in open field. In more than half of the vinyl house soils surveyed, electric conductivity was more than 4.0 mmhos/cm and available phosphate was more than 1,000ppm. 2. Contents of availble phosphate and exchangeable potassium were increased with years of cultivation and their content of accumulation in soil were in the order of Bunpyong-dong>Shinchon-dong>Gageum-myeon>Chilgeum-dong. While their mobility was comparatively low. 3. $NO_3$-N content was remarkably higher in vinyl house soil and the older in cultivation made $NO_3$-N content higher same as the case of available phosphate content. However easy leaching of $NO_3$-N through soil profile is expected due to the fact that $NO_3$-N content was rapidly decreased by removal of polyethylene film cover from the frame of house after harvest of crops. 4. It is a tendency that various chemical contents of vinyl house soils wer higher in 1992 than in 1988~1990, especially much higher from the area of Bunpyong-dong and Shinchon-dong of Cheongju. 5. Salt accumulation in vinyl house soil has been increased with continuing cultivation. Therefore amount of fertilizer application should be controlled in order to avoid salt toxicity, quality deterioration for crop and salt contamination of ground water.