• Korean Journal of Agricultural Science
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• v.17 no.1
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• pp.45-51
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• 1990

This study was conducted to obtain basic data for the design of cooling system by the test of engine performance of the power tiller being used widely in the rural area. Among the various factors affecting engine performance, the flow rate of cooling water was considered as the major factor in this study. Motoring loss, output, fuel consumption ratio, torque, heat absorption of cooling water, and thermal efficiency were measured and analyzed based on three flow rates of cooling water such as 15, 20, and $25{\ell}/min$. The results obtained were as follows : 1. Motoring loss of the engine was 1.371 kW at 2,200 rpm., and mechanical efficiency was 79.1% at rated output level. 2. Output power of the engine increased with the flow rate of cooling water increased. 3. BSFC was 282.9g/kW-h at the flow rate of $20{\ell}/min$, and the temperature of cooling water at outlet was $80.9^{\circ}C$. 4. There was a little variation of torque of the engine depending on the flow rate of cooling water. 5. Absorption of heat by cooling water was increased with the increase of flow rate. 6. The highest thermal efficiency of 32.3% at the flow rate of $20{\ell}/min$ was observed.

• Membrane Journal
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• v.17 no.4
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• pp.294-301
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• 2007

To improve oxidative stability of non-fluorinated styrene-based polymer electrolyte membranes, copolymerized membranes were prepared using styrene derivatives such as p-methylstyrene, t-butylstyrene, and ${\alpha}-methylstyrene$ by monomer sorption method. Prepared membrane was characterized by measurement of weight gain ratio, water content, ion-exchange capacity, proton conductivity, and oxidative stability under the accelerated condition. It was found that each step of monomer sorption method including sorption, polymerization and sulfonation could be affected by the properties and the structures of styrenederivatives. Due to difficulty of polymerization, ${\alpha}$-methylstyrene was copolymerized with styrene or p-methylstyrene. Prepared membrane using ${\alpha}-methylstyrene$ and styrene showed higher performance and stability comparing to copolymerized membrane with styrene. However, copolymerized membranes with ${\alpha}-methylstyrene$ did not showed much improved oxidative stability comparing to styrene membrane due to their lower molecular weight. The t-butylstyrene membrane showed a low performance due to substituted bulky-butyl group which prevents sorption and sulfonation reaction. However, copolymerized t-butylstyrene membranes with p-methylstyrene showed good performance and much improved stability than the styrene membranes.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.1
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• pp.83-91
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• 2018

While using an electrokinetic method to analyze the characteristics of cement solidification of radioactive wastes from decontaminated uranium soil and concrete, the compressive strength, pH, electrical conductivity, irradiation effects, and volume expansion were measured for the solidified cement specimens. The workability of cement solidified from radioactive waste was about 170-190%. After the solidified cement was irradiated, the compressive strength decreased by about 15%, but met the criteria ($34kgf{\cdot}cm^{-2}$) of KORAD (Korea Radioactive Waste Agent). According to the results of SEM-EDS for solidified cement, the aluminum phase was well combined with cement, while the calcium phase was separated from cement. The volume of solidified cement in radioactive wastes was dependent on the waste-to-cement ratio and the amount of water, and increased by about 30% under the conditions used in this study. Therefore, it was concluded that permanent disposal of electrokinetically decontaminated radioactive wastes is appropriate.

• Applied Biological Chemistry
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• v.34 no.3
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• pp.258-261
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• 1991

In order to establish the optimum drying temperature of the heated air blast-grain circulation dryer, a 2 ton scale of paddy was used in this experiment. The temperatures of heated air used were 45, 50, 55, 60, 65 and $70^{\circ}C$. Moisture content of the paddy was reduced to 15% from 24% by drying. The higher air temperature, the shorter drying time and the less fuel consumed. The portion of cracked kernels was found to be low as $3{\sim}10%\;at\;40{\sim}55^{\circ}C$, but was very high to $28{\sim}30%\;at\;60{\sim}70^{\circ}C$. The germination percent was very high as 98 and 93% at 40 and $45^{\circ}C$, but it was decreased to 86 and 30% at 50 and $70^{\circ}C$, respectively. The recovery yield of milled rice from paddy was decreased by 1.76, 2.63 and 7.52% at 60, 65 and $70^{\circ}C$, respectively, compared with 75.86% as drying at $40^{\circ}C$. The higher heated air temperature, the less head rice of milled rice was recovered, and the decreased ratio was increased $60^{\circ}C$. The higher heated air temperature, the less alkali disintergation value and gel consistency of milled rice and the more water up take, expanded vlume, total solid in residual liquid and intensity of starch iodine blue value of residual liquid, and those tendency was found clear from $60^{\circ}C$ temperature of heated air.

• Journal of the Korean Institute of Gas
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• v.20 no.4
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• pp.78-84
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• 2016

In this work, finite element investigations were carried out to optimize reverse drawing process design for manufacture of high-capacity aluminum liner used in fuel cell vehicle. The tensile tests with aluminum alloy Al6061 annealed at $350^{\circ}C$ were carried out to obtain the flow stresses. In order to estimate more accurate flow stresses after necking, the flow stresses were estimated from the comparison of load vs. displacement curves which were obtained from experimental and simulation results of tensile tests. In case of finite element analyses of reverse drawing processes, it was focused on the effects of process designs such as punch and die designs, blank holding force, drawing ratio and the clearance between the punch and blank holder on the generation of wrinkle and fracture of the blank and partially heated punch. However, it was revealed that experimental results still show the fracture at the end of 2nd drawn cup, although partially heated punch is used. Nevertheless, the drawn cup can be used because the sufficient length of the drawn cup for the next flow forming process and spinning process was obtained.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.715-719
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• 2011

The $La_{0.7}Sr_{0.3}Cr_{1-x}Ni_{x}O_{3}$(LSCN-x) perovskites were prepared by citric acid and EDTA using a sol-gel method. The LSCN-x was characterized by BET, XRD, SEM, $H_2$-TPR, EA and TEM. The catalytic performance of LSCN-x catalysts in steam reforming of propane in the temperature range 600~$800^{\circ}C$ was investigated. Propane conversion and hydrogen yield increased with an increase in the amount of added Ni up to x=0.5 in the B-site, denoted as LSCN-0.5, under S/C=1 and S/C=1.7 reaction conditions. The LSCN-0.5 catalyst exhibited the best performance under Ni-substitution of which propane conversion and hydrogen yield was 100%, 95.9% at $800^{\circ}C$ in the S/C=1.7 condition, respectively. The morphology of carbon deposited on the catalysts after reaction exhibited filamentous carbon and amount of carbon deposited on the catalysts after reaction increased with an increase in the amount of added Ni.

• Journal of Sensor Science and Technology
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• v.6 no.5
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• pp.369-375
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• 1997

$V_{2}O_{5}/ThO_{2}/Pd$-doped $SnO_{2}$ sensor has a good selectivity and stability to CO at high sensor temperature of about $500^{\circ}C$, and shows rapid response. In particular, many kinds of interference gases, such as $NO_{x}$, $C_{3}H_{8}$, $CH_{4}$ and $SO_{2}$ have been found to give only a slight influence on the sensor selectivity to CO gas sensitivity by doped $V_{2}O_{5}$ (3.0 wt.%). For the sensor we used well-known thick film technological route with $V_{2}O_{5}$(3.0 wt.%), Pd(1.0 wt.%) and $ThO_{2}$(l.5 wt.%) as catalytic materials. In the case of mixed $NO_{x}$-CO gases, as combustion exhaust gas, only CO detection by $SnO_{2}$ type semiconductor sensor is generally very difficult because of $NO_{x}$ interference. The developed sensors can use to measure the exhausting gas of the automobile or the boiler for the Air-to-Fuel ratio control.

• Proceedings of the KSEEG Conference
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• 2002.10a
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• pp.53-67
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• 2002

As in the past, we are concerned today with the magnitudes of mineral resources and the adequacy of these resources to meet future needs. In looking at global resource issues, we should consider the need for the resource, its supply, and the environmental consequences of using it. The need for a resource can become a resource dependency, specially as the global population expands and each of us becomes Increasingly dependent upon hundreds of natural materials. Therefore, our great mineral consumption makes the human population a true “Geologic Force”, which will be even more significant in the future when the global population is projected to reach alarming proportions. Although our supplies of mineral resources probably will be sufficient for the 21st century, the uneven distribution of minerals in the Earth's crust almost certainly will continue to be a major problem. The most likely result will be major shifts in both prices and sources of supply of many mineral resources. As for energy resources, we must avoid an obsessive dependency on one fuel and expand instead to other energy resources. Finally, because the use of resources affects the environment, we need to focus on resource exploitation and global pollution, particularly in regard to ground water and arable land. We must manage our resources so as to be in balance with our environment. And the accelerated industrialization of South Korean economy over the last three decades has resulted in the mass consumption of mineral commodities. South Korea has around 50 useful mineral commodities for the mineral industry, among 330 kinds of minerals described. The component ratio of the mining industry sector of the gross national production(GNP) in South Korea dropped from 1.2% in 1971 to 0.34% in 1997 due to the rapid growth of other industries in the country. During the period from 1971 to 1997, the average growth rate of mineral consumption in South Korea was 9.13% yearly and that of GMP per capita was 14.97%. The mineral consumptions per capita showed a continual increase during the last 30 years as follows(parenthesis: GW per capita); 0.99 metric tons in 1997($289), 3.83 metric tons in 1989($5, 210), 6.11 metric tons in 1995 ($10, 037), and 6.66 metric tons in 1997($9, 511). The total amount of mineral consumption in South Korea was 33 million tons of 32 mineral commodities in 1971, and 306 million metric tons of 47 mineral commodities in 1997.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.2
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• pp.151-158
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• 2010

In order to measure the deposition velocity of $I_2$ vapor for radish plants and its translocation factor for their roots, radish plants were exposed to $I_2$ vapor for 80 min. at different growth stages between 29 and 53 d after sowing. The exposure was performed in a transparent chamber during the morning time. Deposition velocities ($ms^{-1}$) were on the whole in the range of $1.0{\times}10^{-4}{\sim}2.0{\times}10^{-4}$ showing an increasing tendency with an increase in the biomass density. The results showed some agreement with existing reports that a higher relative humidity would lead to a higher deposition velocity. The acquired deposition velocities were lower than by factors of several tens than some field measurements probably due to a very low wind speed (about $0.2\;ms^{-1}$) in the chamber. Translocation factors (ratio of the total iodine in the roots at harvest to the total plant deposition), estimated in a more or less conservative way, were $1.3{\times}10^{-3}$ for an exposure at 29 d after sowing and $5.0{\times}10^{-3}$ for an exposure at 53 d after sowing. In using the present experimental data, meteorological conditions and chemical and physical forms of iodine need to be carefully considered.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.3
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• pp.193-198
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• 2013

In general, boron recovery of 40-90% could be achieved by Reverse Osmosis (RO) membranes in neutral pH condition. As an emerging technology, Forward Osmosis (FO) membrane has attracted growing interest in wastewater treatment and desalination. The objective of this study is to evaluate the possibility of the boron removal in radioactive liquid waste by FO. In this study, the performance of FO was investigated to remove boron in the simulated liquid waste as the factors such as pH, osmotic pressure, ionic strength of solution, etc. The pH of feed solution is a major operating parameter which strongly influences to the permeation of boron and more than 80% of boron content can be separated when conducted at pH values less than 7. The water flux is not influenced but the boron flux and permeation rate tends to decrease in the low salt concentration of 1,000 mg/L. The boron flux increases linearly, but the permeation ratio of reducing boron is nearly constant even with changes in the draw solution concentration.