• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.114-121
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• 2013

In order to estimate the efficiency of an evaporative heat exchanger having mini channel, the equations to calculate heat exchanger properties, those are air temperatures and water temperatures etc, are derived from the governing equations based on the Navier-Stokes equation, even though there are several assumptions to make problem simplify. There are three heat transfer zones at the mini channel heat exchanger depending on the water condition. So, there are three governing equations and solutions to calculate the properties. As the results of this study, the equations to calculate a saturation point and a dry point are derived to evaluate an evaporative heat exchanger having micro channel. It is supposed to predict and evaluate the performance of a mini channel heat exchanger with evaporation of liquid.

• Current Photovoltaic Research
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• v.9 no.4
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• pp.137-144
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• 2021

In this study, the microstructure of the CVD-fabricated Cu(In,Ga)Se₂ (CIGSe) absorber layer by simulating the stacking sequence used in a co-evaporation method, and changes solar cell performance were investigated. The absorber layer prepared by stacking CuSe and (In,Ga)Se between InSe is separated into Ga-free CuInSe₂ and Ga-rich CIGSe, and transformed to CIGSe by selenization heat treatment with slight improvement in the the solar cell efficiency. However, in CVD, since the supply of liquid Cu-Se is not as active as in the co-evaporation method, the nanoocrystalline layer containing a large amount of Ga remained independently in the absorption layer, which acted as a cause of the loss of J_SC and FF. Therefore, by using a precursor structure in which CuGa is sputter-deposited on a single layer of InSe deposited by CVD, performance parameters of V_OC, J_SC, and FF could be greatly improved.

• Journal of ILASS-Korea
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• v.28 no.1
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• pp.32-42
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• 2023

In this study, spray characteristics of n-heptane and propane were investigated under different injection pressure using various imaging techniques such as Mie-scattering, DBI (diffuse back-illumination), and Schlieren imaging techniques. NI compact RIO system was used to control a test injector. Spray penetration length, length-to-width ratio and number of black pixels were calculated by using MATLAB software to compare spray characteristics of each fuel. Longer spray penetration length and higher length-to-width ratio were observed in propane spray because of flash boiling caused by high saturated vapor pressure. Spray collapse occurred in propane spray due to the high plume-to-plume interaction. Moreover, rapid evaporation occurred in propane spray, so that nozzle tip wetting could not be observed. Rapid evaporation of propane also caused fewer residual droplets compared to n-heptane spray. Therefore, propane is advantageous in reducing the generation of soot emission from large droplets that are not atomized. However, additional evaluation should be conducted considering combustion efficiency and the possibility of deposits by nozzle tip icing during fuel injection.

• Polymer(Korea)
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• v.34 no.6
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• pp.527-533
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• 2010

The pioglitazone loaded poly(lactide-co-glycolide)(PLGA) nanospheres were prepared by emulsion-evaporation method and optimized for particle size and entrapment efficiency. The optimized particles were 125~170 nm in size with narrow size distribution and showed above 85% entrapment efficiency at 30% of pioglitazone loading when prepared with 3% w/v of poly(vinyl alcohol) (PVA) as a surfactant. These particulate carriers exhibited a controlled in vitro release of pioglitazone for 40 days at a nearly constant rate. The pioglitazone loaded PLGA nanospheres were not only effective to reduce the blood sugar level of diabetic rats but also non-toxic for the animal body, in particular for sensitive organs like kidney, liver, heart, lung and spleen. These results indicate that PLGA nanospheres have a great potential for oral delivery of pioglitazone.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.1
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• pp.21-28
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• 2017

Indirect evaporative cooling, which utilizes a cooling effect obtained by the evaporation of water, is energy-effective compared to the conventional vapor compression method. It is also eco-friendly, due to the non-usage of CFC refrigerant. In this study, three indirect evaporative cooler samples of the cross flow type(size: $300mm{\times}300mm{\times}300mm$, channel pitch: $5mm{\times}5mm$, $5mm{\times}7mm$, $7mm{\times}7mm$) were made using plastic/paper composites. Tests were conducted to measure indirect evaporative efficiencies and pressure drops. Results showed that the efficiency was the highest for the $5mm{\times}5mm$ sample, owing to the largest surface area. The saved electrical energy was also the greatest for that sample. The pressure drop of the wet channel was larger than that of the dry channel as expected. A theoretical model was proposed, which underestimated both the indirect evaporation efficiency and the pressure drop.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.83-89
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• 2011

Diesel engines can produce higher fuel efficiency and lower $CO_2$ emission, they are subject to ever more stringent emission regulation. However, there are two major emission concerns fo diesel engines like such as particulate matter (PM) and nitrogen oxides (NOx). Moreover, it is not easy to satisfy the regulations on the emission of NOx and PM, which are getting more strengthened. One of the solutions is to apply the new combustion concept using multistage injection such as HCCI and PCCI. The other solution is to apply after-treatment systems. For example, lean NOx trap catalyst, Urea-SCR and others have various advantages and disadvantages Especially, Urea-SCR system have advantages such as a high conversion efficiency and a wide operation conditions. Hence the key factor to implementation of Urea-SCR technology, good mixing of urea(Ammonia) and gas, reducing Ammonia slip. Urea mixer components are required to facilitate evaporation and mixing because the liquid state of urea poses significant barriers for evaporation, and the distance to mixer is the most critical that affect mixer performance. In this study, to find out the distance from injector to mixer and simulation factor, a laser diagnostics and high speed camera are used to analyze urea injector spray characteristics and to present a distribution of urea solution in transparent manifold In addition, Droplet Uniformity Index is calculated from the acquired images by using image processing method to clarify the distribution of spray.

• Polymer(Korea)
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• v.24 no.5
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• pp.728-735
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• 2000

Fentanyl-loaded biodegradable poly(L-lactide-co-glycolide) (75 : 25 by mole ratio of lactide to glycolide, PLGA) microspheres (MSs) were prepared to study the possibility for long-acting local anesthesia. We developed the fentanyl base (FB, slightly water-soluble)-loaded PLGA MSs by means of conventional O/W solvent evaporation method. The size of MSs was in the range of 10~150 ${\mu}{\textrm}{m}$. The morphology of MSs was characterized by SEM, and the in vitro release amounts of FB were analyzed by HPLC. The lowest porous cross-sectional morphology and the highest encapsulation efficiency were obtained by using gelatin as an emulsifier. The influences of several preparation parameters, such as emulsifier types, molecular weights and concentrations of PLGA, and initial drug loading amount, etc., have been observed in the release patterns of FB. The release of FB in vitro was more prolonged over 25 days, with close to zero-order pattern by controlling the preparation parameters. We also investigated the physicochemical properties of FB-loaded PLGA MSs by X-ray diffraction and differential scanning calorimeter.

• Journal of the Semiconductor & Display Technology
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• v.15 no.1
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• pp.65-69
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• 2016

We have investigated the possibility of recycling of an organic material that is wasted during thermal evaporation. To this end, we have collected a wasted organic material (N,N'-diphenly-N,N'-bis(1,1'-biphenyl)-4,4'-diamine(NPB)) from a vacuum chamber, purified it by recrystallization, and fabricated bilayer organic light-emitting diodes (OLEDs) with the recycled NPB. It is found that the surface roughness of thin films coated with the purified NPB is much enhanced. OLEDs fabricated by thermal evaporation of the purified NPB show lower device efficiency than OLEDs with the original NPB. However, the power efficiency of OLED fabricated by spin coating of the purified NPB is comparable with that of OLED with the original NPB. Therefore, such a recycling method by recrystallization would be more suitable for solution-processed OLEDs.

• Resources Recycling
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• v.21 no.6
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• pp.39-44
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• 2012

An attempt to recover copper from electroless plating wastewater has been made through evaporation followed by the electrowinning method. From the determination of each element in electroless plating wastewater, the content of Cu was found to be 582 mg/l and small amount of Fe was also contained in it. Moreover, the content of COD and TOC which was resulted from the addition of Rochell salt was found to be 9,560 and 13,100 mg/l, respectively. The content of formic acid generated by the oxidation of formaldehyde was determined to be 7.73 %. As a result, current efficiency was decreased with increase in current density and therefore current density less than $40mA/cm^2$ should be maintained to obtain current efficiency more than 80 %. The content of Fe in Cu obtained by electrowinning was found to be 0.021 and 0.01 % at the concentration of sulfuric acid of 2 and 10 vol%, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.6
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• pp.84-93
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• 2018

Three-dimensional (3D) numerical simulations have been carried out to study how coolant injection conditions influence the cooling efficiency and projectile ejection performance in a mixture-gas ejection system (or gas-steam launch system). The 3D single-phase computational model was verified using a 1D model constructed with reference to the previous research and then a two-phase flow computation simulating coolant injection on to hot gas was performed using a DPM (Discrete Phase Model). As a result of varying the coolant flow rate and number of injection holes, cooling efficiency was improved when the number of injection holes were increased. In addition, the change of the coalescence frequency and spatial distribution of coolant droplets caused by the injection condition variation resulted in a change of the droplet diameter, affecting the evaporation rate of coolant. The evaporation was found to be a critical factor in the design optimization of the ejection system by suppressing the pressure drop while the temperature decreases inside the breech.