• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.6
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• pp.449-469
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• 2011

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering during 2010. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends of thermal and fluid engineering have been surveyed as groups of general thermal and fluid flow, fluid machinery, and new and renewable energy. Various topics were presented in the field of general thermal and fluid flow. Research issues mainly focused on the thermal reliability of axial fan and compressor in the field of fluid machinery. Studies on the design of ground source heat pump systems and solar chemical reactors were executed in the field of new and renewable energy. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (3) Refrigeration systems with alternative refrigerants such as hydrocarbons, mixed refrigerants, and CO2 were studied. Performance improvement of refrigeration systems are tried applying various ideas of refrigerant subcooling, dual evaporator with hot gas bypass control and feedforward control. The hybrid solar systems combining the solar collection devices with absorption chillers or compression heat pumps are simulated and studied experimentally as well to improve the understanding and the feasibility for actual applications. (4) Research trend in the field of mechanical building facilities has been found to be mainly focused on field applications rather than performance improvements. Various studies on heating and cooling systems, HVAC facilities, indoor air environments and energy resources were carried to improve the maintenance and management of building service equipments. In the field of heating and cooling systems, papers on a transformer cooling system, a combined heat and power, a slab thermal storage and a heat pump were reported. In the field of HVAC facilities, papers on a cooling load, an ondol and a drying were presented. Also, studies on HVAC systems using unutilized indoor air environments and energy resources such as air curtains, bioviolence, cleanrooms, ventilation, district heating, landfill gas were studied. (5) In the field of architectural environment and energy, studies of various purposes were conducted such as indoor environment, building energy, renewable energy and green building. In particular, renewable energy and building energy-related researches have mainly been studied reflecting the global interest. In addition, many researches which related the domestic green building certification of school building were performed to improve the indoor environment of school.

• Journal of Environmental Impact Assessment
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• v.22 no.2
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• pp.171-181
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• 2013

In this study, we report the water quality characteristics of pollutants for 4 major tributaries in the Yeongsan and Sumjin river basins using statistical analysis, such as regression equation and factor analysis. The flow rate and water qualtiy data collected from 4 sampling sites(Hwangryoung A, Jiseok A, Chooryeong A, Osu A) in the Yeonsan and Sumjin river basin during the past 3 years were analyzed for 11 parameters(flow rate, dissolved oxgen, pH, water temperature, electric conductivity, biochemical oxygen demand, chemical oxygen deman, total organic carbon, total nitorgen, total phosphorus, suspended solid). The results showed that the concentrations of BOD, COD, TOC, T-N, T-P in Hwangryoung A(HW) and Jiseok A(JS) of the Yeongsan river basin were decreased as the flow rate was increased. This means that rather than nonpoint soources, point sources affect water quality. In the cases of Chooryeong A(CR) and Osu A(OS) in the Sumjin river basin, howerever, nonpoint sources than point sources are an important factor that affects the water quality. Also, the factor analysis technique was employed to analyze principal component influencing on water quality. The results revealed that the first principal component in HW was correlated with EC, DO, T-N, water temperature. This "nitrogen influx according to seasonal pattern" factor may be interpreted. In JS, the first principal component was correlated with BOD, COD, TOC and is likely to represent "organic matter" processes. In CR and OS, BOD, COD, TOC, SS and T-P were significantly correlated and is considered as representing "Organic matter and adsorption of phosphorus on sediments influx". This study is expected to contribute to the effective pollution control/management of the surfac waters in the study sites.

• Journal of Korea Water Resources Association
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• v.41 no.2
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• pp.149-162
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• 2008

The Soil and Water Assessment Tool (SWAT) developed by the USDA-Agricultural Research Service for the prediction of land management impact on water, sediment, and agricultural chemical yields in a large-scale basin was applied to Daecheong Reservoir basin to estimate the amount of soil losses from different land uses. The research outcomes provide important indications for reservoir managers and policy makers to search alternative watershed management practices for the mitigation of reservoir turbidity flow problems. After calibrations of key model parameters, SWAT showed fairly good performance by adequately simulating observed annual runoff components and replicating the monthly flow regimes in the basin. The specific soil losses from agricultural farm field, forest, urban area, and paddy field were 33.1, $2.3{\sim}5.4$ depending on the tree types, 1.0, and 0.1 tons/ha/yr, respectively in 2004. It was noticed that about 55.3% of the total annual soil loss is caused by agricultural activities although agricultural land occupies only 10% in the basin. Although the soil erosion assessment approach adopted in this study has some extent of uncertainties due to the lack of detailed information on crop types and management activities, the results at least imply that soil erosion control practices for the vulnerable agricultural farm lands can be one of the most effective alternatives to reduce the impact of turbidity flow in the river basin system.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.401-408
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• 2014

In membrane bio-reactor (MBR), the aeration control is one of the important independent variables to decrease fouling and to save energy with shear stress change on the membrane surface. The paper was carried out for numerical simulation of 3-dimensional fluid flow phenomena of the cylindrical bioreactor with submerged flat membranes equipped in the center and supplied the air from the bottom by using the COMSOL program. The viscosity and temperature of solution were assumed to be constant, and the specific air demand based on permeate volume ($SAD_p$) defined as scouring air per permeate rates was used as a variable. The calculated CFD velocities were compared with those of the velocity meter measurement and video image analysis, respectively. The results were good agreement each other within 11% error. For fluid flow in the reactor the liquid velocity increased rapidly between the air diffuser and membrane module, but the velocity decreased during flowing of the membrane module. Also, the velocity increased as it was near from the reactor wall to the central axis. The calculated shear stress on the membrane surface showed the highest value at the center part of the module bottom side and increased as aeration rate increased. Especially, the wall shear stress increased dramatically as the aeration rate increased from 0.15 to 0.25 L/min.

• Clean Technology
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• v.16 no.4
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• pp.277-283
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• 2010

Eosin Y is used a colorant and dye but eosin Y is harmful toxic substance. In this study, the adsorption characteristics of granular activated carbon have been investigated for the adsorption of eosin dye dissolved in water. The effects of initial dye concentration, contact time, pH and temperature on adsorption of eosin by a fixed amount of activated carbon have been studied in batch adsorber and fixed bed. The adsorptivity of activated carbon for eosin Y were largely improved by pH control. When the pH was 3 in the sample, the eosin Y could be removed 99% of initial concentration (10 mg/L). The adsorption equilibrium data are successfully fitted to the Freundlich isotherm equation in the temperature range from 293 to 333 K. The estimated values of k and ${\beta}$ are 19.56-134.62, 0.442-0.678, respectively. The effects of the operation conditions of the fixed bed on the breakthrough curve were investigated. When the inlet eosin Y concentration is increased from 10 to 30 mg/L, the corresponding adsorption breaktime appears to decrease from 470 to 268 min at bed height of 3 cm and a constant flow rate of 2 g/min. When the initial eosin Y flow rate is increased from 1 to 3 g/min, the corresponding adsorption breaktime appears to decrease from 272 to 140 min at bed height of 3 cm and inlet concentration of 10 mg/L. Also, breaktime increased with increasing bed height at flow rate of 2 g/min and inlet concentration of 10 mg/L. And length of adsorption zone showed similar patterns.

• Korean Journal of Ecology and Environment
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• v.33 no.1 s.89
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• pp.23-30
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• 2000

n situ sediment oxygen demand (SOD), which takes place with the uptake of dissolved oxygen for biological metabolism and chemical oxidation in sediments, ranged from 1.57 to $12.55\;mg\;O_2\;m^{-2}\;h^{-1}$ in onshore of Lake Paldang from April to November 1999. SOD was influenced by the amount of organics and oxygen diffusion. Comparing the oxygen demands partitioning between overlying water and sediment during initial phase, SOD accounted for $63.8{\sim}94%$ of total oxygen demand in Lake Paldang. The chemical SOD and nitrogenous oxygen demand ranged $1.2{\sim}18.3%$ and $8.3{\sim}51.7%$ of total SOD, respectively. This result indicated that SOD in Lake Paldang occurred mainly by aerobic respiration and nitrification. Although the flow velocity could increase SOD within a certain limit, the effect of sediment depth on SOD was dependent on physicochemical properties of the sediment. This study showed that SOD can represent a significant portion of the total oxygen up-take in Lake Paldang. Therefore, the assessment of SOD might be necessary for the control of water quality.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.257-263
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• 2019

Lightweight geopolymers were fabricated with non-milled IGCC slag and Si sludge as a bloating material. The relationship between addition amount of Si sludge and physical/chemical properties of lightweight geopolymers was investigated. When the geopolymers were made by mixing IGCC slag, alkali activator, and more than 10 wt.% Si sludge, the temperature of the geopolymer pastes reached higher than 130℃ in a few minutes. This exothermic reaction accelerated the geopolymer reaction; however, it was difficult to make geopolymer specimens because of a rapid bloating reaction. Both compressive strength and density of the specimens tend to decrease with an addition of Si sludge; however, there was little difference in both compressive strength and density with addition of Si sludge more than 10 wt.%. Because there was a limit to get low density geopolymers by simply increasing the addition of Si sludge, the control of pore size and distribution of geopolymer is more important by controlling flow rate of the paste through the control of W/S ratio. Therefore, it is important to control process conditions, appropriate W/S ratio for the bloating than the control of Si sludge. The optimum W/S ratio was 0.20 for the addition of Si sludge less than 30 wt.% and W/S ratio should be more than 0.28 for the addition of Si sludge more than 30 wt.%, although there was no practical application in fact.

• Journal of Periodontal and Implant Science
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• v.28 no.4
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• pp.601-611
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• 1998

Ion irradiation is a very promising tool to modify the chemical structure and physical properities of polymers. This study was aimed to evaluate the cellular adhesion to ion beam-irradiated surface of biodegradable poly-l-lactide(PLLA) membrane. The PLLA membrane samples were irradiated by using 35 KeV $Ar^+$ to fluence of $5{\times}10^{13}$, $5{\times}10^{14}$ and $5{\times}10^{15}\;ion/cm^2$. Water contact angles to control and each dose of ion beam-irradiated PLLA membranes were measured. Cultured fetal rat calvarial osteoblasts were seeded onto control and each dose of ion beam-irradiated PLLA membranes and cultured. After 24 hours, each PLLA membranes onto which osteoblasts attached were examined by scanning electron microscopy(SEM). Osteoblasts were removed from each PLLA membrane and then, the vitality and the number of cells were calibrated. Alkaline phosphatase of detached cells from each PLLA membranes were measured. Ion beam-irradiated PLLA membranes showed no significantly morphological change from control PLLA membranes. In the measurement of water contact angle to each membrane, the dose range of ion beam employed in this study reduced significantly contact angles. Among them, $5{\times}10^{14}\;ion/cm^2$ showed the least contact angle. The vitalities of osteoblastes detached from each membranes were confirmed by flow cytometer and well attached cells with their own morphology onto each membranes were observed by SEM. A very strong improvement of the cell adhesion and proliferation was observed for ion beam-irradiated surfaces of PLLA membranes. $5{\times}10^{15}\;ion/cm^2$ exhibited the most strong effect also in cellular adherence. ALPase activities also tended to increase in ion beam-irradiated membranes but statistical differences were not found. These results suggested that ion beam irradiation is an effective tool to improve the adhesion and spreading behaviour of the cells onto the biodegradable PLLA membranes for the promotion of membrane-tissue integration.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.588-596
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• 2006

The surface of polystyrene membrane treated by Ar, $O_2$ plasma, and the effects were observed before and after the treatment and permeability of $CO_2$, $N_2$ and selectivity of $CO_2$ relative to $N_2$ was measured using continuous flow gas permeation analyzer (GPA). The mole ratio of O over C in the surface was increased from 0 to 0.179 with Ar plasma treatment and route mean square of surface was increased from $15.86{\AA}$ to $71.64{\AA}$. Therefore the contact angle was decreased from $89.16^{\circ}$ to $18.1^{\circ}$. Thus Plasma treatments made surface of membrane tend to be highly hydrophilic. The optimum condition for the $CO_2$ permeability and ideal selectivity of the plasma treated membrane was as follows: the measurement of Ar (60 W, 2 min, $70^{\circ}C$) plasma treatment was $1.14{\times}10^{-12}[m^3(STP){\cdot}m/m^2{\cdot}sec{\cdot}atm]$ and 4.22. In the case of $O_2$ plasma treatment, the contact angle was decreased at $13.56^{\circ}$ with increase of O/C ratio ($0.189{\AA}$) and route mean square of surface ($57.10{\AA}$). The optimum condition for the $CO_2$ permeability and ideal selectivity of the plasma treated membrane was as follows: the measurement of $O_2$ (90 W, 2 min, $70^{\circ}C$) plasma treatment was $7.1{\times}10^{-12}[m^3(STP){\cdot}m/m^2{\cdot}sec{\cdot}atm]$ and 11.5. After plasma treatment, the changes of membrane surface were all subtly linked with both cross-linking and etching effects. Finally, it was confirmed that the gas permeation capacity and selectivity of the modified membrane with plasma could be improved by an appropriate control of the plasma conditions such as treatment time, the power input and sort of plasma gas.

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.42-46
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• 2017

As $CO_2$ emission with imprudent using fossil fuel, annual mean temperature of earth is increased in every year. Geothermal energy is inexhaustible energy resource to solve this problem. Heat pump performance and heat exchange efficiency of ground loop are important to distribute widely. Thus, this study are performed to increase heat pump performance and heat exchange efficiency of ground loop with dual expansion valves and spacer. As a results, COP of cooling & heating is obtained improvement up to 11.4% using dual expansion valves, and heat exchange efficiency is increased up to 17.5% using spacer. It will be reduced initial installation cost due to increasing heat pump performance and heat exchange efficiency of ground loop.