• Journal of ILASS-Korea
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• v.10 no.2
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• pp.18-31
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• 2005

This study was performed to explore the liquid breakup and atomization characteristics for the classification of drop formation mode and background of uniform droplets generation in electrohydrodynmaic atomization according to the change of experimental parameters such as nozzle material (stainless steel. teflon). fluid flow rate, applied electrical field and intensity, and frequency. In results, from the classification map of drop formation modes according to the variation of applied AC voltage and frequency at a stainless nozzle, the droplet size was smaller than the outer diameter of the nozzle tip relatively in the spindle mode. The transition points became clearly to be moved toward the high applied voltage by rising the applied AC frequency beyond 450Hz. Also the droplet radius can be observed quite small in the frequency bandwidth of $350{\sim}450Hz$. The droplet radiuses decrease as the applied voltage increases for a fixed applied AC frequency within the range from 50Hz to 400Hz Over 400Hz, the relation between the power intensity and the droplet size was not consistent with a continuous mechanism of liquid breakup. Thus, it is showed that the droplet size distribution using the teflon nozzle was analogous to the results of stainless steel, but the droplet size was bigger than that of stainless steel relatively in case of a teflon nozzle.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.6
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• pp.526-529
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• 2006

The aim of this study was to prepare cyclosporin A-loaded liposome (CyA-Lip) as an oral delivery carrier, with their encapsulation into microspheres based on alginate or extracellular polysaccharide (EPS) p-m10356. The main advantage of liposomes in the microspheres (LIMs) is to improve the restricted drug release property from liposomes and their stability in the stomach environment. Alginate microspheres containing CyA-Lip were prepared with a spray nozzle; CyA-Liploaded EPS microspheres were also prepared using a w/o emulsion method. The shape of the LIMs was spherical and uniform, and the particle size of the alginate-LIMs ranged from 5 to $10\;{\mu}m$, and that of the EPS-LIMs was about $100\;{\mu}m$. In a release test, release rate of CyA in simulated intestinal fluid (SIF) from the LIMs was significantly enhanced compared to that in simulated gastric fluid (SGF). In addition, the CyA release rates were slower from formulations containing the liposomes compared to the microspheres without the liposome. Therefore, alginate-and EPS-LIMs have the potential for the controlled release of CyA and as an oral delivery system.

• Korean Journal of Metals and Materials
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• v.50 no.10
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• pp.763-768
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• 2012

The uniform and highly smooth nanofibers of biocompatible poly(${\varepsilon}$-caprolactone) (PCL) composited with different contents of multiwalled carbon nanotubes (MWCNTs) were successfully prepared by electrospinning. Experimental parameters were MWCNTs addition to a PCL solution and applied voltages. The topographical features of the composite nanofibers were characterized by scanning electron microscopy and its electrical properties were measured by a four-point probe method. The surface resistance gradually decreased with an increasing content of MWCNTs in PCL fibers because of the excellent electrical conductivity of MWCNTs. The nanofiber diameter could be regulated by varying the solution viscosity and voltages. Our results establish that this kind of electrospinning PCL/MWCNTs nanofibers with the control of fiber diameter and electrical conductivity may be a promising candidate for the application of scaffolds in tissue engineering.

• Journal of Drive and Control
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• v.20 no.3
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• pp.25-34
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• 2023

In this study, we conducted a research on optimizing the spraying performance of agricultural drones and predicted the spraying performance in various flight conditions using the multi-layer perceptron (MLP). Data was collected using a test device for pesticide spraying performance according to the water sensitive paper (WSP) evaluation. MLP training involved supervised learning to achieve a coefficient of variation (CV), which indicates the degree of uniform spraying. The performance evaluation was conducted using R-squared (R²), the test samples showed an R² of 0.80. The results of this study showed that drone spraying performance can be predicted under various flight environments. In addition, the correlation analysis between flight conditions and predicted spraying performance will be useful for further research on optimizing the spraying performance of agricultural drones.

• Journal of Ceramic Processing Research
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• v.18 no.11
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• pp.810-814
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• 2017

Proton exchange membrane fuel cells (PEMFCs) are some of the most efficient electrochemical energy sources for transportation applications because of their clean, green, and high efficiency characteristics. The optimization of catalyst layer morphology is considered a feasible approach to achieve high performance of PEMFC membrane electrode assembly (MEA). In this work, we studied the effect of the solvent on the catalyst layer of PEMFC MEAs fabricated using the electrostatic spray deposition method. The catalyst ink comprised of Pt/C, a Nafion ionomer, and a solvent. Two types of solvent were used: isopropyl alcohol (IPA) and dimethylformamide (DMF). Compared with the catalyst layer prepared using IPA-based ink, the catalyst layer prepared with DMF-based ink had a dense structure because the DMF dispersed the Pt/C-Nafion agglomerates smaller and more homogeneously. The size distribution of the agglomerates in catalyst ink was confirmed through Dynamic Light Scattering (DLS) and the microstructure of the catalyst layer was compared using field emission scanning electron microscopy (FE-SEM). In addition, the electrochemical investigation was performed to evaluate the solvent effect on the fuel cell performance. The catalyst layer prepared with DMF-based ink significantly enhanced the cell performance (1.2 A cm-2 at 0.5 V) compared with that fabricated using IPA-based ink (0.5 A cm-2 at 0.5 V) due to the better dispersion and uniform agglomeration on the catalyst layer.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.3
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• pp.99-105
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• 2018

In order to avoid un-uniform crystallization on the surface of a quartz glass crucible that is known to affect the production yield of the single crystal silicon, Ba (barium) was selected as a crystallization promotor and the inner surface of the crucible was coated using Ba (barium hydroxide octahydrate)-solution by the spray pyrolysis method. For un-coated crucible, it was found that the crystallization of its surface started at $1350^{\circ}C$, and at $1450^{\circ}C$ the surface was uniformly crystallized with ${\beta}$-cristobalite phase. It was found that the crucible coated with Ba began to be crystallized from $1000^{\circ}C$ and was uniformly crystallized on the crucible surface at $1300^{\circ}C$. In this case, ${\alpha}$-cristobalite and needle-shaped $BaSi_2O_5$ phase were created and disappeared as a crystal phase, and the ${\beta}$-cristobalite phase was eventually evenly distributed over the Ba-coated crucible surface.

• Korean Journal of Agricultural Science
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• v.43 no.3
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• pp.346-352
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• 2016

This study was conducted to obtain the correlation between the plant surface spray adhesion amount of pesticides and the pest control effect. The linearity of the standard curves of dinotefuran and thiodicarb was $R^2=0.9999$, and recovery was between 70% to 120% which was satisfactory for insecticide residue analyses. The pest control effect was evaluated by assessing the number of apple leafminers (Phyllonorycter ringoniella, Gracillariidae, Lepidoptera) captured by sex pheromone traps from late June to late September in 2015. For the adhesion amount, dinotefuran recovered from trap A and B, respectively were $47{\mu}g/50cm^2$ and $23{\mu}g/50cm^2$, which can be characterized as a very low adhesion amount in comparison to the average adhesion amount of $81{\mu}g/50cm^2$ in the field. In case of thiodicarb, $691{\mu}g/50cm^2$ and $71{\mu}g/50cm^2$ were recovered from trap A and B, respectively, and the average amount in the field is $325{\mu}g/50cm^2$. These results showed close correlation with the insect population captured by trap A and B. The numbers of insects captured by trap A and B between the end of July and late August were similar. After spraying thiodicarb on August 28, the number of apple leafminers captured by trap B is bigger than that of trap A. It appears that pest occurrence tended to be high at low adhesion amounts of the active ingredient. Therefore, in order to obtain an optimal control effect, it is suggested that uniform application of insecticides is critical instead of relying on the amount of insecticide applied in the field.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.35.1-35.1
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• 2011

New photovoltaic (PV) materials and manufacturing approaches are needed for meeting the demand for lower-cost solar cells. The prototypal thin-film photovoltaic absorbers (CdTe and $Cu(In,Ga)Se_2$) can achieve solar conversion efficiencies of up to 20% and are now commercially available, but the presence of toxic (Cd,Se) and expensive elemental components (In, Te) is a real issue as the demand for photovoltaics rapidly increases. To overcome these limitations, there has been substantial interest in developing viable alternative materials, such as $Cu_2ZnSnS_4$ (CZTS) is an emerging solar absorber that is structurally similar to CIGS, but contains only earth abundant, non-toxic elements and has a near optimal direct band gap energy of 1.4~1.6 ev and a large absorption coefficient of ${\sim}10^4\;cm^{-1}$. The CZTS absorber layers are grown and investigated by various fabrication methods, such as thermal evaporation, e-beam evaporation with a post sulfurization, sputtering, non-vacuum sol-gel, pulsed laser, spray-pyrolysis method and electrodeposition technique. In the present work, we report an alternative method for large area deposition of CZTS thin films that is potentially high throughput and inexpensive when used to produce monolithically integrated solar panel modules. Specifically, we have developed an aqueous chemical approach based on chemical bath deposition (CBD) with a subsequent sulfurization heat treatment. Samples produced by our method were analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, absorbance and photoluminescence. The results show that this inexpensive and relatively benign process produces thin films of CZTS exhibiting uniform composition, kesterite crystal structure, and good optical properties. A preliminary solar cell device was fabricated to demonstrate rectifying and photovoltaic behavior.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.41-48
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• 2014

A urea-SCR system suffers from some issues associated with the ammonia slip phenomenon, which mainly occurs because of the shortage of evaporation and thermolysis time, and this makes it difficult to achieve an uniform distribution of injected urea. A numerical study was therefore performed by changing such various parameters as installed injector angle and application and angle of mixer to enhance evaporation and the mixing of urea water solution with exhaust gases. As a result, various parameters were found to affect the evaporation and mixing characteristics between exhaust gas and urea water solution, and their optimization is required. Finally, useful guidelines were suggested to achieve the optimum design of a urea-SCR injection system for improving the DeNOx performance and reducing ammonia slip.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.205-208
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• 2014

Here, we reported mass-produced organic nanowires with uniform sizes based on poly(9,9-dioctylflurorene) (PFO), poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), (regioregular poly(3-hexylthiophene) (P3HT) which are well known as organic semiconductors for opto/electronics applications, using a melt-assisted wetting method with anodic alumina membrane. The conjugated polymer nanowires showed uniformed diameters (D=250~300 nm) and lengths ($L={\sim}30{\mu}m$) with defect free smooth surface regardless of a kinds of semiconductors. In addition, the nanowires were uniformly deposited onto glass substrates by spray-coating method. Under the UV light irradiation, PFO and F8BT nanowires showed blue and yellow emissions, respectively.