• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.54-61
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• 2001

It is reported that during the cold starting, especially in gasoline engine, the engine response and the effect of HC emission can be improved by prompting atomization and reducing the quantity of fuel adhered to the range of injector tip, inlet port, and inlet valve. The purposes of this study are to promote atomization of fuel before air-fuel mixture in the inlet port. In order to achieve its goal, the glow plug is to evaluate the feasibility of for the early fuel evaporator and the spray behavior characteristics of gasoline, injected on the surface of glow plug with room temperature(2$0^{\circ}C$) and high temperature(25$0^{\circ}C$) is to examine. Particle motion analysis system(PMAS) was used to measure the SMD and the dropsize distribution of impinging spray and free spray. The results of this experiment, evaporation rate of impinging spray was higher than that of free spray, and the higher evaporation rate win, the smaller peak dropsize was. Especially, during early spray SMD of impinging spray was still smaller than that of fee spray.

• Journal of the Korean Applied Science and Technology
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• v.36 no.2
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• pp.609-622
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• 2019

When the surfactant is dissolved in an aqueous solution, it forms aggregate called micelles (<20 nm) in the solution, and micelles can form the solubilized formulation by supporting the active ingredient therein. Swollen micelles are formulations capable of carrying larger amounts of active ingredient than conventional solubilized formulations at 50~100 nm. Unlike liposomes or nanoemulsions, which require a separate process such as high pressure emulsification, Swollen micelle is a more efficient method of solubilization and particle formation from a productive point of view. In this study, stabilization experiments on swollen micelle formulations were carried out using poloxamer 407, and then optimized formulation experiments for tocopheryl acetate components were performed using Response Surface Methodology (RSM). Tocopheryl acetate, a surfactant that affects solubilization and an active substance, were set as a factor and the correlation between them was confirmed. As the evaluation method, stability and particle size distribution and size were confirmed by temperature and time, and the structure and shape of the swollen micelle carrying the active ingredient were confirmed by FIB. These results show that poloxamer 407 0.500%, octyldodeceth-16 0.387% and tocopheryl acetate 0.945% are the most optimized prescriptions for swollen micelle stabilized with tocopheryl acetate.

• Journal of the Korean Applied Science and Technology
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• v.37 no.6
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• pp.1738-1751
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• 2020

The skin is divided into three parts: the epidermis, the dermis, and the subcutaneous fat, and the stratum corneum, which is located at the top of the epidermis, acts as a barrier that prevents drug delivery. Nanoemulsions are known to be effective in transdermal delivery of drugs through intercellular lipids because of their unique small particle size. In this study, phase inversion temperature (PIT) nanoemulsion containing α-bisabolol was optimized using response surface methodology (RSM) for effective skin absorption of α-bisabolol. As a preliminary experiment, the 25-2 fractional factorial design method and the 23 full factorial design method were performed. Box-Behnken design was performed based on the results of the factorial design method. The content of surfactant (6.3~12.6%), co-surfactant (5.2~7.8%) and α-bisabolol (0.5~5.0%) were used as factors, and the dependent variable was the particle size of the nanoemulsion. PIT nanoemulsion optimization was performed according to the RSM results, and as a result, the optimal nanoemulsion formulation conditions were predicted to be 10.4% surfactant content, 6.3% co-surfactant content, and 5.0% α-bisabolol content. As a result of the skin absorption test, the final skin absorption rate of the PIT nanoemulsion was 35.11±1.01%, and the final skin absorption rate of the general emulsion as a control was 28.25±1.69%, confirming that the skin absorption rate of the PIT nanoemulsion was better.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.383-391
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• 2019

Bio-grouting based on microbial-induced calcite precipitation (MICP) is recently emerging as a novel and environmentally friendly technique for improvement of coarse-grained ground. To date, the mechanical behaviour of bio-grouted coarse-grained soil with different calcite contents and grain sizes still remains poorly understood. The primary objective of this study is to investigate the influence of calcite content on the mechanical properties of bio-grouted coarse-grained soil with different grain sizes. This is achieved through an integrated study of uniaxial loading experiments of bio-grouted coarse-grained soil, 3D digitization of the grains in conjunction with discrete element modelling (DEM). In the DEM model, aggregates were represented by clump logic based on the 3D morphology digitization of the typical coarse-grained aggregates while the CaCO₃ was represented by small-sized bonded particle model. The computed stress-strain relations and failure patterns of the bio-grouted coarse-grained soil were validated against the measured results. Both experimental and numerical investigation suggest that aggregate sizes and calcite content significantly influence the mechanical behaviour of bio-cemented aggregates. The strength of the bio-grouted coarse-grained soil increases linearly with calcite content, but decreases non-linearly with the increasing particle size for all calcite contents. The experimental-based DEM approach developed in this study also offers an optional avenue for the exploring of micro-mechanisms contributing to the mechanical response of bio-grouted coarse-grained soils.

• Korean Journal of Materials Research
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• v.28 no.1
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• pp.12-17
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• 2018

$In_2O_3$ doped $WO_3$ powders were prepared by a polymer solution route and their $NO_2$ gas sensing properties were analyzed. The synthesized powders showed nano-sized particles with specific surface areas of $6.01{\sim}21.5m^2/g$ and the particle size and shape changed according to the content of $In_2O_3$. The gas sensors fabricated with the synthesized powders were tested at operating temperatures of $400{\sim}500^{\circ}C$ and 100~500 ppm concentrations of $NO_2$ atmosphere. The particle size and $In_2O_3$ content affected on the initial sensor resistance in an air atmosphere. The highest sensitivity (8.57 at $500^{\circ}C$), which was 1.77 higher than the sensor consisting of the pure $WO_3$ sample, was measured in the 0.5 mol% $In_2O_3$ doping sample. In addition, the response time and recovery time were improved by the addition of $In_2O_3$.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.2
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• pp.193-202
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• 2015

The determining the appropriate dosage of coagulant is very important, because dosage of coagulant in the coagulation process for wastewater affects removing the amount of pollutants, cost, and producing sludge amount. Accordingly, in this study, in order to determine the optimal PAC dosage in the coagulation process, CCD (Central composite design) was used to proceed experimental design, and the quadratic regression models were constructed between independent variables (pH, influent turbidity, PAC dosage) and each response variable (Total coliform, E.coli, PSD (Particle size distribution) (< $10{\mu}m$), TP, $PO_4$-P, and $COD_{cr}$) by the RSM (Response surface methodology). Also, Considering the various response variables, the optimum PAC dosage and range were derived. As a result, in order to maximize the removal rate of total coliform and E.coli, the values of independent variables are the pH 6-7, the influent turbidity 100-200 NTU, and the PAC dosage 0.07-0.09 ml/L. For maximizing the removal rate of TP, $PO_4$-P, $COD_{cr}$, and PSD(< $10{\mu}m$), it is required for the pH 9, the influent turbidity 200-250 NTU, and the PAC dosage 0.05-0.065 ml/L. In the case of multiple independent variables, when the desirable removal rate for total coliform, E.coli, TP, and $PO_4$-P is 90-100 % and that for $COD_{cr}$ and PSD(< $10{\mu}m$) is 50-100 %, the required PAC dosage is 0.05-0.07 ml/L in the pH 9 and influent turbidity 200-250 NTU. Thus, if the influent turbidity is high, adjusting pH is more effective way in terms of cost since a small amount of PAC dosage is required.

• Composites Research
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• v.21 no.2
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• pp.15-24
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• 2008

In this study, shear thickening fluid (STF) filled with rigid nano silica particles was impregnated in plain woven Kevlar fabrics to improve the impact resistance performance. The nano silica particles with an average diameter of 100nm, 300nm, and 500nm were used to make shear thickening fluid to estimate the effect of particle size on the impact behavior of STF impregnated Kevlar fabrics. The yam pull-out and frictional tests were conducted to estimate the effect of impregnated STF on the frictional characteristics. The test results showed that the friction forces were dramatically increased at the STF onset shear strain rates that were measured in preliminary rheology tests. The low speed impact tests were performed using the drop test machine. The results showed that the impregnated STF improved the impact resistance performance of the Kevlar fabrics in terms of the impact energy absorption and the deformation. It has been shown through tests that the impregnated STF affects the interfacial friction which contributes to improve the energy absorption in the Kevlar fabrics. Especially, the impregnation of the STF with the smaller particle size into the Kevlar fabrics showed the better performance in impact energy absorption.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.204-204
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• 2010

A development of device with reduced size and improved sensitivity is highly impotant Pb(Zr,Ti)$O_3$ thin films are widely used both to make actuator and sensor due to their high sensitivity and low cost. In this study, the feasibility of a piezoelectric presssure sensors based on hybrid low-temperaute co-fired ceramic (LTCC) technology were presented. The LTCC diaphragms with thickness of $400\;{\mu}m$ were fabricated by laminating 4 green tapes which consist of alumina and glass particle in an organic binder. PZT thin films were successfully prepared on between top and bottom Au electrode with LTCC substrates using RF magnetron sputtering. In addition, The frequency response characteristics of the sensor under varing pressure has been analysed. by Network Analyser (HP-8722D). A frequency shift range has been obseved from 1.7GHz to 1.8GHz with a good linearity for applied pressure from 0 psi up to 25 psi.

• Journal of Mushroom
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• v.21 no.3
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• pp.110-117
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• 2023

Cordycepin (3'-deoxyadenosine) is a nucleoside analog known for its diverse range of biological activities. This study investigated the effect of different types of sawdust on the production of the bioactive compound cordycepin. The results of the study showed that different types of wood sawdust affected the biosynthesis of cordycepin and a significant increase was observed when the conventional SDB medium was replaced with 1% NaOH treated pine sawdust. To optimize cordycepin production from Paecilomyces tenuipes in a medium containing 1% NaOH-pretreated pine sawdust, we employed Response Surface Methodology (RSM) in its Box-Behnken design (BBD) canonical form. The optimal conditions were determined as follows: a particle size of 109.5111-mesh (140 ㎛) for 1% NaOH-pretreated pine sawdust, an input weight of 21.1679 g/L, and an incubation time of 73.8423 hours. According to our model, this combination is expected to yield a maximum cordycepin content of 896.1428 ㎍/mL. Experimental validation of this prediction was performed using the suggested optimal conditions, resulting in an average cordycepin content of 922.6771 ㎍/mL across three replicates, thus confirming the model's accuracy.

• Particle and aerosol research
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• v.10 no.2
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• pp.53-59
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• 2014

Palladium (Pd) nanoparticles attached graphene (GR) composite was synthesized for an enhanced glucose biosensor. Aerosol spray pyrolysis (ASP) was employed to synthesize the GR-Pd composite using a colloidal mixture of graphene oxide (GO) and palladium chloride ($PdCl_2$) precursor. The effects of the weight ratio of the Pd/GR on the particle properties including the morphology and crystal structure were investigated. The morphology of GR-Pd composites was generally the shape of a crumpled paper ball, and the average composite size was about $1{\mu}m$. Pd nanoparticles less than 20 nm in diameter were deposited on GR sheets and the Pd nanoparticles showed clear crystallinity. The characteristic of the glucose biosensor fabricated with the as-prepared GR-Pd composite was tested through cyclic voltammetry measurements. The biosensor exhibited a high current flow as well as clear redox peaks, which resulted in a superior ability of the catalyst in terms of an electrochemical reaction. The highest sensitivity obtained from the amperometric response of the glucose biosensor was $14.4{\mu}A/mM{\cdot}cm^2$.