• Analytical Science and Technology
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• v.35 no.2
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• pp.41-52
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• 2022

The leaching of nitrate from soil increases the concentration of elements, such as nitrogen, phosphorus, and potassium, in water, causing eutrophication. In this study, the feasibility of using clinoptilolite as an ion-exchange material to reduce nitrate leaching in soil was investigated. Soil samples were collected from three soil depths (0 - 30, 30 - 90, and 90 - 120 cm), and their sorption capacity was determined using batch experiments. The effects of contact time, initial concentration, adsorbent dosage, pH, and temperature on the removal of NO₃^- were investigated. The results showed that an initial concentration of 25 mg L^-1, a contact time of 120 min, an adsorbent dosage of 5.0 g/100 mL, a pH of 3, and a temperature of 30 ℃ are favorable conditions. The kinetic results corresponded well with a pseudo-second-order rate equation. Intra-particle diffusion also played a significant role in the initial stage of the adsorption process. Thermodynamic studies revealed that the adsorption process is spontaneous, random, and endothermic. The results suggest that a modification of clinoptilolite effectively reduces the leaching of nitrate in soil.

• IEMEK Journal of Embedded Systems and Applications
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• v.18 no.1
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• pp.9-17
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• 2023

This paper relates to the development of a device for measuring the efficiency of a solar panel based on a variable constant current, and proposed a standard for reuse of the solar panel. By applying a variable constant current circuit to a solar panel efficiency measuring device, it was easy to apply a maximum power point tracking (MPPT) algorithm. In addition, a load dispersion method was applied to measure the efficiency of a high-capacity solar panel. and it is possible to solve a problematic thermal runaway during a MOSFET parallel operation by applying the load dispersion method. As a result of the experiment, the solar panel efficiency measuring device was able to accommodate a large solar panel of 350W, which is the maximum measurement goal. In this paper, the validity was confirmed through the 310W solar panel efficiency measurement experiment collected after removal.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.785-792
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• 2024

This article provides an overview of the design methodology used to develop a conceptual set of reactivity control mechanism of a micro reactor based on the U-Battery. The U-Battery is based on remote deployment and therefore it is favourable to provide a long fuel lifecycle. This is achieved by implementing a high fissile loading content, which proves challenging when considering reactivity control methods. This article follows the design methodology used to overcome these issues, with an emphasis on a new concept of a moveable moderator which utilises the size of the U-Battery as a small reduction in moderation provides a significant reduction in reactivity. The latest work on this project sees the moveable moderator investigated during a depressurised loss of forced coolant accident, where a reduction of moderator volume increases the maximum fuel temperature experienced. The overall conclusion is that the maximum fuel temperature is not significantly increased (4 K) due to the central reflector region relatively lower volumetric heat capacity compared to that of whole core. However, a small temperature increase is observed immediately after the transient due to the central reflector removal because it reaches energy equilibrium with the fuel region faster.

• Journal of the Korea Organic Resources Recycling Association
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• v.4 no.2
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• pp.55-62
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• 1996

The purpose of this study is the evaluation of adsorption capacity of casts for heavy metals comparing with the activated carbon. The casts was obtained from vermicomposting of the mixed organic sludges which were generated from the treatment facilities for leather wastewater and cattle wastewater. The physico-chemical characteristics of cast was investigated. Also, the batch adsorption experiments of cast and activated carbon for heavy metals were carried out, and the results were analyzed by Freundlich isotherm. The buffering capacity to the acidic wastewater was founded in the cast, and the cation exchange capacity of cast impling adsorption capacity for soluble substances was evaluated as about 55me/100g. Those were implied that the cast have a large potential as a good adsorbent for soluble pollutants in wastewater. From the results of batch experiments, the removal efficiencies of tested various heavy metals including Pb, Cu, Cd, and Cr were very high value as 89-98% for the activated car-bon, and 80~95% for the casts except for Zn. The adsorption equilibriums for the two materials were achieved within 90 minutes. The order of preferable metals in the adsorption was found to be Pb>Cu>Cd>Cr>Zn on the cast and to be Pb>Cd>Cu>Cr>Zn on the activated carbon, respectively. From the above results, it might be con-cluded that cast is effectively available as a good adsorbent to treating the heavy metal bearing wastewater.

• Nuclear Engineering and Technology
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• v.27 no.4
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• pp.470-482
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• 1995

The Ulchin 3&4, which are 2825 MWt PWRs, adopted Safety Depressurization System (SDS) to mitigate the beyond design basis event of Total Less of Feedwater(TLOFW). In this study the results and methodology of the analyses for the determination of SDS bleed capacity are discussed. The SDS design bleed capacity has been determined from the CEFLASH-4AS/REM simulation according to the following design criteria : 1) Each SDS flow path, in conjunction with one of two High Pressure Safety Injection (HPSI) pumps, is designed to have a sufficient capacity to prevent core uncovery if one SDS path is opened simultaneously with the opening of the Pressurizer Safety Valves (PSVs). 2) Both SDS bleed paths are designed to have sufficient total capacity with both HPSI pumps operating to prevent core uncovery if the Feed and Bleed (F&B) initiation is delayed up to thirty minutes from the time of the PSVs lift. To verify the results of CEFLASH-4AS/REM simulation a comparative analysis kas also been per-formed by more sophisticated computer code, RELAP5/MOD3. The TLOFW event without operator recovery and TLOFW event with F&B are analyzed. The predictions by the CEFLASH-4AS/REM of the transient too phase system behavior are in good qualitative and quantitative agreement with those by the RELAP5/MOD3 simulation. Both of the results of analyses by CEFLASH-4AS/REM and RELAP5/MOD3 have demonstrated that decay heat removal and core inventory make-up can be successfully accomplished by F&B operation during now event for the Ulchin 3&4.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.10
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• pp.986-993
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• 2010

In this study, sorption characteristics of thermally treated activated alumina (AA) for fluoride were investigated. Sorption experiments have been conducted in equilibrium and kinetic batch conditions. Also, effects of solution pH and anions on fluoride removal have been observed. The properties of thermally treated ( $700^{\circ}C$) activated alumina (AA700) and untreated activated alumina (UAA) were compared using field-emission scanning electron microscope, energy-dispersive spectrometry, X-ray diffractometer (XRD) analysis, and Brunauer-Emmett-Teller (BET) analysis. From the experiments using AA thermally treated at different temperatures (100, 300, 500, $700^{\circ}C$), it was found that at high fluoride concentrations (50, 100, 200 mg/L) the sorption capacity of thermally treated AA increased with increasing thermal treatment temperature. At an initial fluoride concentration of 200 mg/L, the sorption capacity of AA700 was 3.67 times greater than that of UAA. The BET analysis showed that the specific surface area of UAA was about 2 times larger than that of AA700. The XRD analysis indicated that UAA was composed of both boehmite (AlOOH) and bayerite ($Al(OH)_3$) while AA700 was $Al_2O_3$. The reason that fluoride sorption capacity of AA700 increased despite of decrease in specific surface area compared to UAA could be attributed to the change of crystal structure. The kinetic sorption test showed that fluoride sorption to AA700 arrived at equilibrium after 24 h. The equilibrium test demonstrated that the maximum sorption capacity of AA700 was 5.70 mg/g. Additional batch experiments indicated that fluoride sorption to AA700 was the highest at pH 7, decreasing at both acidic and basic solution pHs. Also, fluoride sorption to AA700 decreased in the presence of anions such as phosphate, nitrate, and carbonate. This study demonstrated that thermal treatment of AA at high temperature could increase its sorption capacity for fluoride.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.9
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• pp.747-752
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• 2009

This research was performed by means of several different virgin granular activated carbons (GAC) made of each coal, coconut and wood, and the GACs were investigated for an adsorption performance of bromate in a continuous adsorption column. Breakthrough behavior was investigated that the breakthrough points of the virgin two coals-, coconut- and wood-based GACs were observed as 9252 bed volume (BV), 6821 BV, 5291 BV and 2431 BV, respectively. The experimental results of adsorption capacity (X/M) for bromate showed that two coal- based GACs were highest (1334.5 and 798.2 ${\mu}g$/g), the coconut-based GAC was intermediate (668.6 ${\mu}g$/g) and the wood-based GAC was lowest (156.8 ${\mu}g$/g). The X/M of the coal-based GACs was 2~8.5 times higher than the X/M of the coconut-based and wood-based GACs. The results of carbon usage rates (CURs) for the virgin two coal-, coconut- and wood-based GACs were shown as 0.19, 0.25, 0.33 and 0.71 g/day respectively. The adsorption capacity, k values, were also investigated by means of the GACs for bromate. The k values of two coal-, coconut- and wood- based GACs for bromate were found to be 121.3, 76.7, 43.3 and 14.6 respectively. This results suggested that using the virgin GAC made of coal was the best selection for removal of bromate in the water treatment for an advanced treatment.

• Journal of Soil and Groundwater Environment
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• v.17 no.2
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• pp.54-61
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• 2012

In this study, the adsorption of $Cu^{2+}$ from aqueous solution by the biochar derived from woody biomass at different pyrolysis temperatures has been investigated. The woody biomass wastes used in this study were branch of willow ($Salix$ $koreensis$ $Andersson$) and bark of chestnut ($Castanea$ $crenata$ $var.$ $dulcis$). Three biochar samples prepared by heating each biomass at temperature of $300^{\circ}C$, $500^{\circ}C$, and $700^{\circ}C$were tested for the adsorption capacity of Cu. Also the physicochemical properties of the developed biochars were studied using different characterization techniques such as FT-IR, SEM, BET surface area, and cation exchange capacity (CEC). The adsorption of Cu could be well described by Langmuir model for both willow and chestnut biochars with $R^2{\geq}0.98$. The maximum adsorption capacities of the biochar produced at $700^{\circ}C$ from the Langmuir equation were found to be 12.5 mg $g^{-1}$ and 16.9 mg $g^{-1}$ for willow and chestnut, respectively. Chestnut biochar was found to interact more effectively with the active sites available for Cu, resulting higher removal of Cu(II) than wiloow biochar. Ion exchange and surface complexation found to be the main mechanisms involved in the adsorption process. This study demonstrated the feasibility of the biochars derived from woody biomass to be as a low-cost potential adsorbent for heavy metals as Cu(II) removal in aquatic system.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.2097-2104
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• 2000

Naturally occurring taste and odor problems include those produced by microorganism. notably algae and bacteria. The major compounds causing taste and odor are MIB and Geosmin which can cause earthy-musty at very low concentration 9ng/L and 4ng/L, respectively. Especially, the problem is very serious from summer to fall in source and finished water. It is well known that using PAC is one of the best technology to control these compounds in drinking water treatment. In this study, optimum dosage and dosing time of PAC were observed with the adsorption isotherm experiments in single and binary compounds. Also, the effect of natural organic matter(NOM) was investigated by using a natural water with JSW. The adsorption capacity of Geosmin was higher than MIB in both with NOM and without NOM. The adsorption capacity of Geosmin and MIB was 4 times lower with NOM than that of without NOM. which was caused by competition adsorption. When the initial concentration of Geosmin and MIB were 100ng/L in JSW, at least 4 hours of reaction time was needed to achieve 99% removal with 20mg/L of the PAC.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.216-222
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• 2002

With deterioration of the nation's infrastructure comes the growing, need for effective means of rehabilitating structures. Possibly one for the most challenging tasks is to upgrade the overall capacity of concrete structure. Therefore, considerable efforts are still being made to develop new construction materials. Rehabilitation of damaged RC structures occasionally requires the removal and replacement of concrete in the tension zone of the structural members. Typical situation where the tension zone repair is necessary is when the concrete in the tension zone in beams or slabs has spalled off as a result of corrosion in the bottom reinforcing bars or due to extensive fire. The rehabilitation of such conditions normally involves the removal of the concrete beyond the reinforcement bars, cleaning or replacing the tensile bars and reinstatement of concrete to cover the steel bars the original shape and size. This study focused on the flexural behavior of reinforced concrete beams strengthened by steel strand and carbon fiber sheet in the tension zone. The properties of beams are 15$\times$25 cm rectangular and over a 200cm span. Test parameters in this experimental study were strengthening methods, jacking volume, the number of sheet. We investigated the flexural behavior of simply supported RC beams which are strengthened with the carbon fiber sheet, monotonic loads. Attention is concentrated upon overall bending capacity, deflection, ductility index, failure mode and crack development of repaired and rehabilitated beams.