• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.2
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• pp.57-62
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• 2000

The photocatalytic degradation of trichloroethylene(TCE) in water on various types of$TiO_2$ was studied. Surface properties of $TiO_2$were characterized by XRD, SEM, and BET in our previous work(23) . $TiO_2$from Aldrich has 100$\%$pure anatase, TiO$_2$from KIER has 100$\%$ pure rutile structure, and P25-TiO$_2$from Degussa has mixed structure of anatase(75$\%$) and rutile(25$\%$) . Firstly, optimum conditions for TCE degradation were examined in this study. Results showed that optimum loading amount of catalyst was 0.1 wt% and recirculation flow rate of mixture(distilled water and TCE) was 200 cc/min. Secondly, the effect of $TiO_2$structure on TCE degradation was examined. Results revealed that anatase structure generally has better photocatalytic activity than rutile structure. Especially, mixed structure(Degussa P25-$TiO_2$) has the highest activity due to small particle size and large specific surface area.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.573-580
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• 2005

This study was to investigate the removal characteristics of toluene in a gas stream by using a biotrickling filter packed with zeolite-contained polyethylene media. The specific surface area and the void fraction of the media were $500\;m^2/m^3$ and 82%. The surface roughness of the media was higher than that of pure polyethylene media. The toluene removal efficiency decreased with increasing the inlet toluene concentration and gas flow rate. The maximum elimination capacity of toluene in the biotrickling filter was $64\;g/m^3{\cdot}hr$. During 200 days operation, toluene removal efficiency was maintained from 90% to 98% until 167 days, hereafter, it was rapidly reduced with a rise in pressure drop due to an excess proliferation of biomass on the media. Pressure drop and removal capability of the biotrickling filter was fully recovered after backwashing.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.96-101
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• 2012

An experimental study was conducted to investigate the performance of a concentrating photovoltaic cell (CPV) against temperature. It is know that a high efficiency of a CPV can be achieved only with proper cell temperature as well as high concentration ratio (CR). This study is concerned with appropriate cooling condition for a liquid-convection cooler for the best performance of a specific CPV. A series of experiments was conducted in a range of cell temperatures as a result of varying cooling conditions, while the concentration ratio was 390 and the solar irradiation flux was higher than 900 $W/m^2$ in outdoor environment. The CPV had a planar dimension of 10 by 10 mm. A Fresnel lens was used as a concentrator, of which the dimension was 221 mm(W) ${\times}$ 221 mm(L) ${\times}$ 3 mm(t) and the transmissivity was known to be 0.8. The cooler was attached to the bottom side of the CPV and had a contact area of 21 mm(W) ${\times}$ 26 mm(L), which was identical to the size of the base plate of the CPV. The coolant temperature was controlled by an isothermal bath and the flow rate was controlled and measured by a flowmeter. The experimental results showed that the average of power efficiency of the CPV decreased from 28.6 % to 24.7 % as the cell temperature increased from $36^{\circ}C$ to $97^{\circ}C$. An appropriate cooling method of a CPV might increase the power conversion efficiency by about 4% for the same concentration ratio. Discussion is included from the viewpoint of the combined efficiency in addition to the power efficiency.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.1
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• pp.1-13
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• 2010

A comparative study between a computation and an experiment has been conducted to predict the performance of a Pod type waterjet for cm amphibious wheeled vehicle. The Pod type waterjet has been chosen on the basis of the required specific speed of more than 2500. As the Pod type waterjet is an extreme type of axial flow type waterjet, theoretical as well as experimental works about Pod type waterjets are very rare. The main purpose of the present study is to validate and compare to the experimental results of the Pod type waterjet with the developed CFD in-house code based on the RANS equations. The developed code has been validated by comparing with the experimental results of the well-known turbine problem. The validation also extended to the flush type waterjet where the pressures along the duct surface and also velocities at nozzle area have been compared with experimental results. The Pod type waterjet has been designed and the performance of the designed waterjet system including duct, impeller and stator was analyzed by the previously mentioned m-house CFD Code. The pressure distributions and limiting streamlines on the blade surfaces were computed to confirm the performance of the designed waterjets. In addition, the torque and momentum were computed to find the entire efficiency and these were compared with the model test results. Measurements were taken of the flow rate at the nozzle exit, static pressure at the various sections along the duct and also the nozzle, revolution of the impeller, torque, thrust and towing forces at various advance speed's for the prediction of performance as well as for comparison with the computations. Based on these measurements, the performance was analyzed according to the ITTC96 standard analysis method. The full-scale effective and the delivered power of the wheeled vehicle were estimated for the prediction of the service speed. This paper emphasizes the confirmation of the ITTC96 analysis method and the developed analysis code for the design and analysis of the Pod type waterjet system.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.67-72
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• 2006

Precipitated calcium carbonate (PCC) was prepared in a cylindrical reactor by the nozzle spouting method. The reactor was filled with $CO_2$ and $Ca(OH)_2$ suspensions were circulated through a nozzle to prepare PCC. This method has several advantages such as provision of large contact area between suspension and $CO_2$ and production of large number of nuclei in short time. By changing suspension concentrations, suspension temperature, flow rates of $CO_2$ and nozzle sizes, PCC from homogeneously dispersed $0.1{\mu}m$ to heterogeneous $0.3{\mu}m$ can be obtained. According to XRD analyses, most PCC formed was calcite with small amount of aragonite depending on the reaction conditions. Usually, the reaction proceeded at high pH and electric conductivities initially. Then, pH and electric conductivities decreased rapidly to the saturation condition. Results indicated that the specific conditions (temperature: $25^{\circ}C$, suspension concentration: 0.5 wt%, $CO_2$ flow rate: 1 L/min, nozzle size: 0.4 mm) were required to prepare uniform particle size (particle diameter: $0.1{\mu}m$) of PCC.

• Science of Emotion and Sensibility
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• v.15 no.1
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• pp.1-8
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• 2012

There have been many emotion researches to investigate physiological responses on specific emotions with physiological parameters such as heart rate, blood volume flow, and skin conductance. Very few researches, however, exists by detecting them with facial skin temperature. The purpose of present study was to observe the differences of facial skin temperature by using thermal camera, when participants stimulated by monitor scenes which could evoke fear or joy. There were totally 98 of participants; undergraduate students who were in their adult age and middle, high school students who were in their adolescence. We measured their facial temperature, before and after presenting emotional stimulus to see changes between both times. Temperature values were extracted in these regions; forehead, inner corners of the eyes, bridge of the nose, end of the nose, and cheeks. Temperature values in bridge and end of the nose were significantly decreased in fear emotion stimulated. There was also significant temperature increase in the area of forehead and the inner corners of the eyes, while the temperature value in end of the nose decreased. It showed decrease in both stimulated fear and joy. These results might be described as follows: When arousal level going up, sympathetic nervous activity increases, and in turn it makes blood flow in peripheral vessels under the nose decrease. Facial temperature changes by fear or joy in this study were the same as the previous studies which measured temperature of finger tip, when participants experiencing emotions. Our results may help to develop emotion-measuring techniques and establish computer system bases which are to detect human emotions.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.227-234
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• 2022

In this study, the rheological properties of cement paste composites applied with carbon-based nano-materials were experimental analyzed. Flow table and rheological properties, compressive strength were measured in the cement paste using graphene oxide asqueous solution and carbon nanotube aqueous solution. When carbon nano-materials was mixed in an aqueous solution, flow decreased and plastic viscosity and shear stress were increased. In particular, graphene oxide rapidly increased the plastic viscosity and shear stress. In the case of carbon nanotube aqueous solution, when less than 0.2 % was mixed, the increase rate was low compared to graphene oxide. This is because the specific surface area of graphene, which is in the form of a plate, is large. The compressive strength showed a small amount in strength increase when graphene mix, and CNT had a strength about 112 % of OPC. Carbon-based nanomaterials, is considered that CNT are suitable more to be used construction materials. However, extra studies on the surfactant to be used for mixing proportion and dispersion will be needed.

• The Journal of Engineering Geology
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• v.12 no.2
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• pp.215-234
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• 2002

Groundwater Dam is one of the reliable techniques to get huge amount of groundwater abstraction for municipal, agricultural, drinking, industrial water supply system. It can be a major technique to solve water shortage problems when it based on the sufficient watershed, proper topology, and adequate aquifer distribution and pollution control, Groundwater Dam had initiated its construction by RDC(former KARICO) in early eighties in Korea and 4 of it in total were added more until late eighty. However, this technique has shrunken its application due to gradually decreased yield rate after sever years of construction. After we studied several existing sites precisely, we concluded that the main reason of decreasing yield rate was come form engineering roughness on construction in early nineties. Theoretically, the technique itself seemed to be little detectives however, there were a little application in the fields in Korea. With the recent advance in engineering fields, those defects in construction would be no longer obstacle to construct underground wall and the technique could be a one of major ground water production technique in the future. It is essential to study following items thoroughly before select the appropriate site. The topography and the site of the underground wall, aquifer distribution, the specific technique for wall construction to block groundwater flow effectively and strict quality control during construction are critical. The surface and ground water monitoring data should be collected. Sustainability of the Groundwater Dam with huge groundwater abstraction in long term should be based on the long-term water balance analysis for each site. The water quality, environmental effect analysis and maintenance achedule should be also analyzed and planned in prior. It is suggested that the two consecutive underground wall in the coastal area to prevent seawater intrusion beneath a single wall.

• Economic and Environmental Geology
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• v.53 no.6
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• pp.667-675
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• 2020

An Alum-sludge based adsorbent (ASBA) was synthesized by the hydrothermal treatment of alum sludge obtained from settling basin in water treatment plant. ASBA was applied to remove fluoride and arsenic in artificially-contaminated aqueous solutions and mine drainage. The mineralogical crystal structure, composition, and specific surface area of ASBA were identified. The result revealed that ASBA has irregular pores and a specific surface area of 87.25 ㎡ g-1 on its surface, which is advantageous for quick and facile adsorption. The main mineral components of the adsorbent were found to be quartz(SiO2), montmorillonite((Al,Mg)2Si4O10(OH)2·4H2O) and albite(NaAlSi3O8). The effects of pH, reaction time, initial concentration, and temperature on removal of fluoride and arsenic were examined. The results of the experiments showed that, the adsorbed amount of fluoride and arsenic gradually decreased with increasing pH. Based on the results of kinetic and isotherm experiments, the maximum adsorption capacity of fluoride and arsenic were 7.6 and 5.6 mg g-1, respectively. Developed models of fluoride and arsenic were suitable for the Langmuir and Freundlich models. Moreover, As for fluoride and arsenic, the increase rate of adsorption concentration decreased after 8 and 12 hr, respectively, after the start of the reaction. Also, the thermodynamic data showed that the amount of fluoride and arsenic adsorbed onto ASBA increased with increasing temperature from 25℃ to 35℃, indicating that the adsorption was endothermic and non-spontaneous reaction. As a result of regeneration experiments, ASBA can be regenerated by 1N of NaOH. In the actual mine drainage experiment, it was found that it has relatively high removal rates of 77% and 69%. The experimental results show ASBA is effective as an adsorbent for removal fluoride and arsenic from mine drainage, which has a small flow rate and acid/neutral pH environment.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.38-43
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• 2022

The effect of introducing oxygen functional groups by oxygen plasma treatment of activated carbon on adsorption properties of cesium ions was investigated. During the oxygen plasma treatment, the frequency, power, and oxygen gas flow rates were fixed at 100 kHz, 80 W, and 60 sccm, respectively, while the reaction time was varied. Under the experimental conditions, the amount of cesium ion adsorption increased as the content of oxygen groups on C-O-C and O=C-O bonds increased when the reaction time with oxygen gas was 10 minutes. However, when the reaction time increased to 15 minutes, the oxygen functional group content decreased resulting in the decrease of the adsorbed cesium ion amount. On the other hand, unlike the oxygen content of the surface-treated activated carbon, the specific surface area and pore properties were hardly affected by the oxygen plasma reaction time. As a result, the oxygen plasma-treated activated carbon improved the cesium ion removal rate by up to 97.3% compared to that of the untreated activated carbon. This is considered to be due to the content of oxygen groups on C-O-C and O=C-O bonds introduced on the surface of the activated carbon through oxygen plasma treatment.