• 월간산업보건
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• s.8
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• pp.4-30
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• 1988

Examination of working environments was conducted to get more detailed data about harmful working environments and to make a contribution to more effective management. Study was carried out on 722 factories located in Taegu city and eight counties in Kyungpook Province, Korea, for a period of one year, from February 1 to December 30, 1986. The total number and proportion of workers exposed to harmful material was 37,697, 45.2% among 83,368 workers. The results according to exposed material were as follows: 1. In the case of noise, proportion of exceeding the 8-hour TLV was 59%, Included were nail-cutting in assembly metal manufacturing industry and weaving process in textile. 2. Dust in mill process of coal manufacturing industries exceeded the TLV of second class of dust at all parts and exceeded the TLV at 6% as a whole.: 3. The fields of industry lower than 70 lux of illumination were storage equipment of food, auto-winder of textile, painting of wood wares and coal mixing, and 44% of all cases was lower than standard. 4. As a result of temperature index investigation(WBGT), about 12% of all sujects exceeded limit value. Included parts were rolling machine and reducing room. 5. In the case of organic solvents, TLV was exceeded at about 8%, The parts exceeded TLV according to materials belonged to this category were as follows. 1) Toluene: adhesive work in assembly metal manufacturing 2) Xylene: printing and paint mixing in chemical manufacturing 3) Methyl ethytl ketone: paint mixing in all parts examined and coating machine partially in chemical manufacturing 4) Methyl isobutyl ketone: printing in chemical manufacturing 5) Acetone: vapor polishing in assembly metal manufacturing 6. Among specified chemical materials, the concentration of HC1 in the air in metal assembly manufacturing factory exceeded TLV. in one of three assembly metal manufacturing examined. Others, such as benzene, acetic acid, formic acid, sodium hydroxide, formalin, ammonia, copper, chromate etc. were lower than TLV in its indoor atmospheric concentration. As a whole, the proportion of exceeding TLV was about 0.8% 7. The concentrations of inorganic lead were lower than TLV in all parts examined. The results of this investigation show the fact that current management of working environments is not satisfactory, and so more active management is needed.

• Journal of Bio-Environment Control
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• v.16 no.2
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• pp.108-114
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• 2007

This study was conducted to clarify the effects of the different mixing ratios of substrate mixtures based on peat moss and the concentration of nutrient solution on the growth of tomato (Lycopersicon esculentum Mill.) seedlings. Substrates such as peat moss, rice hull, carbonized rice hull, decomposed sawdust, perlite and granular rock wool were mixed and used. The concentration of nutrient solution were adjusted to EC $0.5{\sim}1.5mS/cm$. The volumetric moisture contents became higher as peat moss mixed were much more. Total porosities in all substrate mixtures were over 80%, and pH in substrate mixtures became lower as the volume of peat moss mixed higher. Mixing ratios of substrates suitable for the production of tomato seedlings with the higher quality were peat moss:rice hull:carbonized rice hull:decomposed sawdust:perlite=25:10:25:20:20(v/v). The plant growth was not significant among the different substrate mixtures. However, plant growth such as plant height, leaf area, and total dry weight became significantly increased as EC increasing.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.7
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• pp.488-494
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• 2012

This study was conducted to determine the optimal ratio of sludges from milk processing industry (MPS), paper-mill industry (PMS) and night-soil treatment plant (NSS) for vermicomposting. Five different ratios, 0 : 80 : 20 (MPS-0), 25 : 60 : 15 (MPS-25), 50 : 40 : 10 (MPS-50), 75 : 20 : 5 (MPS-75), and 100 : 0 : 0 (MPS-100 : control) MPS : PMS : NSS by wet weight were tested in a small plot experiment. The experiment for each mixing ratio was performed for 2 weeks with the three replications. MPS-100 (100 : 0 : 0) only had the highest decomposition rate with 19.9%, followed by MPS-25, MPS-50, MPS-75 and MPS-0 with 19.5, 19.1, 17.6 and 16.7%, respectively. Except for MPS-100, Vermicomposting resulted in increase in ash, T-P, $NO_2{^-}-N$, $NO_3{^-}-N$, Mg, K, As, Cd and Cu, whereas moisture, VS (Volatile Substance), TKN (Total Kjeldahl Nitrogen), $NH_4{^+}-N$, Ca, Hg and Pb were lower in the final cast than the initial feed mixture. Meanwhile Zn showed very slight difference and Cr and Ni did not show any tendency between the feed mixture and the final cast. In the case of MPS-100, where the decomposition rate was the highest, all the heavy metals in the final cast except for Hg were increased. All the vermicomposts produced from five different mixing ratios of the vermicomposting sludges met the Korea Standard as by-product compost.

• Applied Biological Chemistry
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• v.46 no.2
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• pp.140-143
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• 2003

This study was performed to develop a more rapid and simple nutrient diagnosis method of plants than the conventional leaf analysis method. tomato (Lycopersicon esculentum Mill. cv. super momotaro) was planted in the mixed media produced by mixing perlite and rock wool at 1 . 1 (v/v) ratio. The Yamazakki nutrient solutions for cucumber and tomato were supplied to the media using the micro-drip irrigation system. Experimental plots produced consisted of no fertilization, deficient fertilization, adequate fertilization and surplus fertilization for N, P and K, respectively. Each experimental plot was replicated four times. Specific color different sensor values (SCDSV) measured by the chlorophyll meter were closely related to total-N concentrations in the leaves measured by the conventional method. Nitrate, $PO_4$ and K concentrations in petiole sap measured by test strips #(Reflectoquant^{\circledR},\;Merck,\;Germany)$ showed a significant relationship with total-N, p and K concentrations in leaves. The linear regression equations between $NO_3,\;PO_4$ and K concentrations in petiole sap and total-N, p and K concentrations in the leaves were prepared. The optimum levels of $NO_3,\;PO_4$ and K in petiole sap were obtained by plugging the optimum concentrations of total-N, p and K in the leaves by other researchers into the equations. In conclusion, the SCDSV by the chlorophyll meter and concentrations of NO3, p and K in petiole sap measured by the test strips would be suitable for rapid estimation of plant nutrient status.

• Composites Research
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• v.27 no.5
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• pp.190-195
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• 2014

This paper predicts the complex permittivity of MWNT added epoxy depending on agglomeration by numerical analysis. 1wt% MWNT added epoxy specimen is prepared using 3-roll-mill method and its complex permittivity is measured in X-band (8.2~12.4 GHz) using freespace measurement system. The analytic model is comprised of cube epoxy and perfect sphere agglomeration. The complex permittivity of the agglomeration model is predicted by complex permittivity mixing rule using the measured complex permittivity of epoxy and 1 wt% MWNT added epoxy. Commercial electromagnetic analysis software, CST, is used to obtain S-parameter of the analytic model and MATLAB code is used to calculate complex permittivity from the S-parameter. It is confirmed that the complex permittivity increases when the agglomeration size decreases.

• The Korean Journal of Food And Nutrition
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• v.16 no.2
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• pp.146-151
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• 2003

Chinese medical materials of Astragalas manbranaceus Bunge, Angelica gigas Nakai, Cnidium officinale, Glycyrrhiza uralensis Fisch, Lycium Chinese Mill were mixed, mixing ratio was 28:20: 18:18:16(w/w). Yield and concentration of extract obtained through extraction- concentration process of the mixed Chinese medical materials were 37.28%(w/w) and 50Brix, respectively. Animal feed(AF) used for animal test was manufactured from both mixing of general AF and this extract(0∼ 5%, w/w) and freeze dried. After the male rats were fed experimental diets in order to test during 4 weeks, the results of plasma TG, total cholesterol, phospholipid content changes and plasma, pancreas and femur insulin concentration changes were followed. The more the amount of treatment of Chinese medical material extract are, the higher the effect of concentration decline are in plasma lipid concentration. And at 3% treatment plasma TG, total cholesterol and phospholipid contents are decreased respectively 8.62%, 2.81% and 2.11%. Plasma glucose concentration has also similar effect that those things are decreased at 3% treatment. Insulin concentration of plasma, pancreas and femur are difficult to prove the effects due to respective increase and decrease. We guess that these results comes from not experimenting intentioned rat of diabetes mellitus but normal rat.

• Asian-Australasian Journal of Animal Sciences
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• v.10 no.2
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• pp.164-169
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• 1997

The present experiment was conducted to evaluate the effects of feed processing and feeding methods on growth performance and carcass characteristics of growing-finishing pigs. A total of 72 pigs (LYD, 22.24 kg BW) were employed for a 90-d feeding trial. Treatments were 1) mash dry feeding (MD), 2) mash wet feeding (MW), 3) pellet dry feeding (PD), and 4) extruded pellet dry feeding (EPD). Corn, soybean meal and wheat bran in the basal diets were extruded before mixing and pelleting for EPD diet production. Ileal or fecal digestibility and carcass traits including lean meat percentage and weights of stomach ulcer were also examined. During the growing period, pigs fed PD showed improved (p < 0.05) average daily gain (ADG) and feed conversion (F/G) over those fed MD, whereas no significant differences in average daily feed intake (ADFI) were found among dietary treatments. Finisher pigs fed MD showed lover, but not significant, ADG and F/G than those fed MW, PD or EPD. For the overall period, pigs fed PD grew faster (p < 0.05) than those fed MD or EPD. Feed intake was different between the two feeding methods (MD vs MW), and between the two processed feeds (PD vs EPD). The digestibility of crude fat was higher (p < 0.05) in pigs fed EPD than in pigs fed mash feeds. NFE digestibility of EPD treatment was also higher (p < 0.05) than that of PD. Back fat (10th rib area) was thicker (p < 0.05) tn pigs fed MD than in pigs fed EPD. other carcass traits including incidence of esophagogastric ulcers were not different among treatments. In conclusion, pelleting appeared to bo the desirable processing methods and wet feeding could also be recommended for growing-finishing pigs.

• Journal of Surface Science and Engineering
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• v.50 no.3
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• pp.198-205
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• 2017

Thermal dissipation was investigated for poly methyl methacrylate (PMMA) composite films containing graphite and multi wall carbon nanotube(CNT) powders as filler materials. After mixing PMMA with fillers, solvent, and dispersant, the pastes were prepared by passing through a three roll mill for three times. The prepared pastes were coated $15{\sim}40{\mu}m$ thick on a side of 0.4 mm thick aluminium alloy plate and dried for 30 min at $150^{\circ}C$ in an oven. The content of fillers in dried films was varied as 1, 2, and 5 weight % maintaining the ratio of graphite and CNT as 1:1. Raman spectra from three different samples exhibited D, G and 2D peaks, as commonly observed in graphite and multi wall CNT. Among those peaks, D peak was prominent, which manifested the presence of defects in carbon materials. Thermal emissivity values of three samples were measured as 0.916, 0.934, and 0.930 with increasing filler content, which were the highest ever reported for the similar composite films. The thermal conductivities of three films were measured as 0.461, 0.523, and $0.852W/m{\cdot}K$, respectively. After placing bare Al plate and film coated samples over an opening of a polystyrene box maintained for 1 h at $92^{\circ}C$, the temperatures inside and outside of the box were measured. Outside temperatures were lower by $5.4^{\circ}C$ in the case of film coated plates than the bare one, and inside temperatures of the former were lower by $3.6^{\circ}C$ than the latter. It can be interpreted that the PMMA composite film coated Al plates dissipate heat quicker than the bare Al plate.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1303-1305
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• 1998

In order to reduce or avoid oxidation problem at operation the interconnects in SOFCs have so far mostly been made of ceramic material. It has high chemical stability both under cathode and anode condition, relatively thermal expansion coefficient that matchs that of electrolyte material YSZ. But this material shown rather weak in the low oxygen atmosphere and thermal shock, and it has lower mechanical strength than alloys. To avoid these problems one may consider to use metals or alloys as materials for interconnects. Metallic interconnects are advantageous because of their high thermal and electronic conductivities. But it has some problems, Those are high thermal expansion and oxidation at high temperature in air. To solve these problems in the interconnection material in this study, $LaCrO_3$-dispersed Cr alloys for metallic interconnector of SOFC have been investigated as a fuction of $LaCrO_3$ content in the range of 5 to 25 vol.%. The Cr alloy were prepared by mixing Cr and $LaCrO_3$ powders in high-energy ball mill for 48h and by sintering under Ar atmosphere with 5vol.% $H_2$ for 10h at $1500^{\circ}C$. The alloys had a relative density of 95% and above. The Cr alloys in composed of two kind of small $LaCrO_3$ and large Cr particles. As the $LaCrO_3$ content increased, the Cr particle size decreased but the $LaCrO_3$ particle size remained contant. Also the oxidation tests show that the $LaCrO_3$-dispersed Cr is very resistant to oxidation in air. These results means that $LaCrO_3$-dispersed Cr is a useful material for metallic interconnect of planar SOFC.

• Journal of Korean Society on Water Environment
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• v.22 no.6
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• pp.996-1003
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• 2006

The absorption characteristics of powdered activated carbon doped by transition-metal nanoparticles were investigated to enhance the remove efficiencies of $TCOD_{Mn}$ and Color from the flexo-inks wastewater. According to the adsorption dynamics of PAC and MPAC, the optimal dosage of activated-carbon adsorbents was 3 g/L under the reaction conditions of pH6.0, 30 mill of reaction time, 240 rpm of mixing intensity. The removal efficiencies by the optimal dosages were maximized as 19% $TCOD_{Mn}$, 57% Color for PAC and 88% $TCOD_{Mn}$, 95% Color for MPAC. Freundlich indexes of isotherm absorption were estimated as follows: i) For PAC, k=-8.11, 1/n=2.98, r=0.91 in the raw water, and k=0.14, b/n=0.75, r=0.96 in the biological treatment water, ii) For MPAC, k=2.69, 1/n=0.21, r=0.80 in the raw water, and k=0.74, 1/n=1.17, r=0.95 in the biological treatment water. MPAC (Powdered activated carbon doped by transition-metal nanoaprticles) was very effective in the removal of organics from the raw water and biological treatment water, as Freundlich indexes of 1/n for both types of water were estimated less than 2.0.